Piggybacking on Brian's comments.
To do this, you should use RR501 transceivers. They are "polite" therefore you avoid both units transmitting at the same time and the commands being lost in powerline collisions. I assume you never plan to use "plug-in" controllers like the "Maxi Console", Mini Console", "Mini Timer", or CM15A and AHP, etc. Any controller that transmits directly to the powerline will bypass the two transceivers and the command will not get coupled to both phases. Also as Brian pointed out, for phase coupling, you are relying on BOTH transceivers, ALWAYS receiving a remotes command. Otherwise, the command will not be coupled to both phases, and that (both tranceivers receiving the remotes signal) may not happen.
In otherwords it will work, but only about as well as a wet band-aid.
Addedum: Sorry paizano1, brain was not fully engaged before I dumped the clutch. As Dave X10 is poining out, you could use one TM751 and one RR501 rather than two RR501's.