I've never thought about that before since during the course of my time in a mechanics shop, I never would've thought to dump battery acid into the oil collection barrel...it just doesn't seem like an easy thing to do (holding an acidic battery, and dumping the contents into the oil, rather than just chucking the whole battery out back?).
That said, I'd think that if something bad was going to happen from the mix of battery acid and oil, it would happen while it was in the barrel and wouldn't spontaneously reanimate (not the right word but you get what I mean) once you centrifuged it. BUT, saying it does get through the centrifuge and doesn't stick to the centrifuge wall, I'm still not too worried about it as long as it's less than 2 microns since it'll either burn up in the cylinder or won't burn up and get pushed out the exhaust as soot.
Over the course of my WMO career I'm sure I've burned at least a couple gallons of stuff that I wasn't sure what it was and so far, no ill effects.
Finally, if the Batt acid won't eat through his filter, my guess is that's because it's inert when it's mixed in with a bunch of oil.