I have just come across the same problem as RootKernel here. It would be nice to have a property where we can set the tile uid so we don't have to have multiples of the same tile map.
I have also noticed some really funky behavior in the latest stable and beta versions of C2, where I start painting on Layer 1 and after i change to layer 2 some of the tiles have been painted on the layer 2 ( rather than layer 1)... I hope that makes sense??