The following map sets enable maps for dungeons that use the same geometry as one of the overlands, using the same map image and the same zone-rect. I'm not far enough along yet to personally test all of them, but Marshlands Miasma is definitely working. The JPG files were taken from the maps.eq2interface.com site.
Code:
<ImageStyle Name="exp20_dun_hooluk_swamp_03_solo" displayname="Splendor Sky Aerie: Marshlands Miasma [Solo]" zonerect="-1295.00, -464.00, 1217.00, 1424.00">
<ImageFrame Source="images/maps/map_exp20_rgn_hooluk.dds" SourceRect="0,0,800,600" />
</ImageStyle>
<ImageStyle Name="exp20_dun_hooluk_swamp_03_easy" displayname="Splendor Sky Aerie: Marshlands Miasma [Event Heroic I]" zonerect="-1295.00, -464.00, 1217.00, 1424.00">
<ImageFrame Source="images/maps/map_exp20_rgn_hooluk.dds" SourceRect="0,0,800,600" />
</ImageStyle>
<ImageStyle Name="exp20_dun_hooluk_invasion_03_solo" displayname="Splendor Sky Aerie: Vale Invasion [Solo]" zonerect="-1295.00, -464.00, 1217.00, 1424.00">
<ImageFrame Source="images/maps/map_exp20_rgn_hooluk.dds" SourceRect="0,0,800,600" />
</ImageStyle>
<ImageStyle Name="exp20_dun_hooluk_invasion_03_easy" displayname="Splendor Sky Aerie: Vale Invasion [Event Heroic I]" zonerect="-1295.00, -464.00, 1217.00, 1424.00">
<ImageFrame Source="images/maps/map_exp20_rgn_hooluk.dds" SourceRect="0,0,800,600" />
</ImageStyle>
<ImageStyle Name="exp20_dun_zimara_breadth_01_solo" displayname="Zimara Breadth: Razing the Razelands [Solo]" zonerect="-1581.00, -1186.00, 1563.00, 1167.00">
<ImageFrame Source="images/maps/map_exp20_rgn_zimara_breadth.dds" SourceRect="0,0,800,600" />
</ImageStyle>
<ImageStyle Name="exp20_dun_zimara_breadth_01_easy" displayname="Zimara Breadth: Razing the Razelands [Heroic I]" zonerect="-1581.00, -1186.00, 1563.00, 1167.00">
<ImageFrame Source="images/maps/map_exp20_rgn_zimara_breadth.dds" SourceRect="0,0,800,600" />
</ImageStyle>
<ImageStyle Name="exp20_dun_zimara_breadth_01" displayname="Zimara Breadth: Razing the Razelands [Heroic II]" zonerect="-1581.00, -1186.00, 1563.00, 1167.00">
<ImageFrame Source="images/maps/map_exp20_rgn_zimara_breadth.dds" SourceRect="0,0,800,600" />
</ImageStyle>
<ImageStyle Name="exp20_dun_zimara_breadth_02_solo" displayname="Zimara Breadth: Strungstone Ascent [Solo]" zonerect="-1581.00, -1186.00, 1563.00, 1167.00">
<ImageFrame Source="images/maps/map_exp20_rgn_zimara_breadth.dds" SourceRect="0,0,800,600" />
</ImageStyle>
<ImageStyle Name="exp20_dun_zimara_breadth_02_easy" displayname="Zimara Breadth: Strungstone Ascent [Heroic I]" zonerect="-1581.00, -1186.00, 1563.00, 1167.00">
<ImageFrame Source="images/maps/map_exp20_rgn_zimara_breadth.dds" SourceRect="0,0,800,600" />
</ImageStyle>
<ImageStyle Name="exp20_dun_zimara_breadth_02" displayname="Zimara Breadth: Strungstone Ascent [Heroic II]" zonerect="-1581.00, -1186.00, 1563.00, 1167.00">
<ImageFrame Source="images/maps/map_exp20_rgn_zimara_breadth.dds" SourceRect="0,0,800,600" />
</ImageStyle>
<ImageStyle Name="exp20_dun_zimara_breadth_03_solo" displayname="Zimara Breadth: Wisdom's Plight [Solo]" zonerect="-1581.00, -1186.00, 1563.00, 1167.00">
<ImageFrame Source="images/maps/map_exp20_rgn_zimara_breadth.dds" SourceRect="0,0,800,600" />
</ImageStyle>
<ImageStyle Name="exp20_dun_zimara_breadth_03_easy" displayname="Zimara Breadth: Wisdom's Plight [Event Heroic I]" zonerect="-1581.00, -1186.00, 1563.00, 1167.00">
<ImageFrame Source="images/maps/map_exp20_rgn_zimara_breadth.dds" SourceRect="0,0,800,600" />
</ImageStyle>
<ImageStyle Name="exp20_dun_aether_wroughtlands_01_solo" displayname="Aether Wroughtlands: Ferric Fields [Solo]" zonerect="-1494.00, -1137.00, 1464.00, 1082.00">
<ImageFrame Source="images/maps/map_exp20_rgn_aether_wroughtlands.dds" SourceRect="0,0,800,600" />
</ImageStyle>
<ImageStyle Name="exp20_dun_aether_wroughtlands_01_easy" displayname="Aether Wroughtlands: Ferric Fields [Heroic I]" zonerect="-1494.00, -1137.00, 1464.00, 1082.00">
<ImageFrame Source="images/maps/map_exp20_rgn_aether_wroughtlands.dds" SourceRect="0,0,800,600" />
</ImageStyle>
<ImageStyle Name="exp20_dun_aether_wroughtlands_01" displayname="Aether Wroughtlands: Ferric Fields [Heroic II]" zonerect="-1494.00, -1137.00, 1464.00, 1082.00">
<ImageFrame Source="images/maps/map_exp20_rgn_aether_wroughtlands.dds" SourceRect="0,0,800,600" />
</ImageStyle>
<ImageStyle Name="exp20_dun_aether_wroughtlands_02_solo" displayname="Aether Wroughtlands: Tarnished Oasis [Solo]" zonerect="-1494.00, -1137.00, 1464.00, 1082.00">
<ImageFrame Source="images/maps/map_exp20_rgn_aether_wroughtlands.dds" SourceRect="0,0,800,600" />
</ImageStyle>
<ImageStyle Name="exp20_dun_aether_wroughtlands_02_easy" displayname="Aether Wroughtlands: Tarnished Oasis [Heroic I]" zonerect="-1494.00, -1137.00, 1464.00, 1082.00">
<ImageFrame Source="images/maps/map_exp20_rgn_aether_wroughtlands.dds" SourceRect="0,0,800,600" />
</ImageStyle>
<ImageStyle Name="exp20_dun_aether_wroughtlands_02" displayname="Aether Wroughtlands: Tarnished Oasis [Heroic II]" zonerect="-1494.00, -1137.00, 1464.00, 1082.00">
<ImageFrame Source="images/maps/map_exp20_rgn_aether_wroughtlands.dds" SourceRect="0,0,800,600" />
</ImageStyle>
<ImageStyle Name="exp20_dun_aether_wroughtlands_03_solo" displayname="Aether Wroughtlands: Chaotic Currents [Solo]" zonerect="-1494.00, -1137.00, 1464.00, 1082.00">
<ImageFrame Source="images/maps/map_exp20_rgn_aether_wroughtlands.dds" SourceRect="0,0,800,600" />
</ImageStyle>
<ImageStyle Name="exp20_dun_aether_wroughtlands_03_easy" displayname="Aether Wroughtlands: Chaotic Currents [Event Heroic I]" zonerect="-1494.00, -1137.00, 1464.00, 1082.00">
<ImageFrame Source="images/maps/map_exp20_rgn_aether_wroughtlands.dds" SourceRect="0,0,800,600" />
</ImageStyle>