Yes, they are all (including Urborg) swamps in addition to any other land type they might have (or don't have in this case). They will keep all their previous abilities and gain "Tap: Add one black mana to your manapool" ability which is granted by the land type Swamp.
August 4, 2014 1:38 a.m.
Draugo nails it.
NB, though - if you're playing City of Brass it will still deal one damage to you as its effect is related to tapping, and not mana production.
August 4, 2014 6:37 a.m.
It works with any land, even Sorrow's Path. (Okay, it works terribly with sorrow's path but you can still make black mana.)