All I can say is the couple PS-1 locos I have with BCRs in them run fine. I do remember reading that there are a small few locomotives, PS-1 and PS-2 that just don't work with BCRs in them, and the only way to find out which locos didn't like them was to put one in. Never heard of the locomotive not working once a MTH rechargeable battery was installed afterwards.
The only other issue I can think of is that there is a possibility someone doesn't let it sit after power up to charge the BCR because either people they are impatient, don't know they need to, or forget they need to and it scrambles the boards.
