Good on them
Good on them. You'd probably have distinct cpe (customer premises equipment) for EPON as rolled out by Verizon for FIOS, and EPON as rolled out by a cable co. then (unless the proper firmware can support both modes of operation.)
But, cable? Some of the cable cos are running their billing systems on a mainframe, it handles billing, sending "hits" to set top boxes (or disabling it as the case may be), provisioning or unprovisioning cable modems, and so on. Using DPoE sounds far easier than trying to come up with a totally new setup for EPON.