Every map can be adopted to a MP setting. However, it takes a lot more creative work. Fitting it to the original, while keeping the theme of how this would transfer to a somewhat realistic feel of a similar setting.
Train is..... well a train, but as you can see, there are plenty of ideas for it.
http://my007heaven.net/gesupdates/B3/2010/19jan/train_full.jpgDam, Frigate, and more are same, but all have a lot of ideas how to make them work.
Caverns_fz could be adopted like the main staircase in Silo. You would get the iconic spiral, while having exits and rooms off of it on different levels. Just one small idea. Its a lot of work, and takes a lot of testing/compiles of hundreds different versions to get a idea fully layed in stone.