Thanks, Rob.

The 15-1995 must have an RF transmitter in it because they tout that as a feature, being able to control your A/V equipment from anywhere in the house. So the base station must be an 'RF rcvr->IR blaster'.
It probably uses a proprietary command set. However, I was thinking that because they document multiple device codes for 'home automation'--including RS P&P, X10, and more), that the RF transmitter might be able to directly send to an X10 transceiver module, et al. in the same way it communicates to the RS base station.
Plus it makes little sense to talk about the RF capability and then have to have an IR rcvr base station to operate X10. Although, that seems to be what they expect with the 15-1994, which also says it can control P&P devices '...with additional hardware'.

Okay, new question: did I read your info correctly where it mentions that the 15-1994 learning remote has a 2K EEPROM, and that the 15-1995 preprogrammed remote has a 1K EEPROM? Does that mean you could 'upgrade' a 15-1995 with the ReplayTV device code the same way you're doing the 1994? If so, then we could create a remote with key mapping, supporting all my (current) equipment, and RF support from any room in the house.
It would be a tough decision to make. Trading off adding A/V control from anywhere in the house and support for X10, versus, having a separate remote for X10.