Although they won't sting each other in the usual manner (so touching is okay), they can chemically inhibit one another. Depending upon your tank size, if you end up with several clones of one BTA and only one of another, the single can show symptoms of failing to thrive (smaller expansion, less aggressive feeding, frequent moving). If this happens, just make sure you target feed the "victim" anemone and things should be fine. Also, running carbon couldn't hurt.
Kevin