Sometimes it works, and sometimes it doesn't. That worked very well at our last house with a transceiver at each end. Since the center of the house was entry, stairwells and bathroom, we never used a remote there. So we didn't have the issue with both transceivers picking up the wireless commands. (One transceiver was a beta CM14A controller, and the other was a RR501).
If two identical transceivers pick up the command simultaneously so they relay those commands to the powerline in perfect synchronization, then they will work well together. Since RF commands are repeated several times, it is possible that one unit will pick up a command before another. If that point straddles a zero crossing of 60Hz, one transceiver can begin transmission a half cycle before the other. In that case, the two transmissions will collide with each other and the command will be corrupted.
Jeff