Based on Ernie's explanation here I can understand why the voltage sense wouldn't work but why would it not work this way:

Hook up a ir emitter to the blaster port and stick the emitter end onto a MS210 (IR sensor) then connect the ir sensor leads to the XP8 with the ground, positive and data wires. I assume these wires would go into the same molex connector on the XP8 as the RM433.
Then could I convert the Macros on the XP8 to IR trigger codes, and dump the appropriate ir trigger code hex into a RTI remote sending standalone ir codes out then learn them to the UPS?

This may in fact work and I may have missed something. I need to go back and look over things more carefully and do some proper testing. I just need more hours in a day.