Perculas are frequently hosted by BTAs. Of course they aren't natural symbiotes, so it's not a guarantee, but odds are pretty good for percs and BTAs. From what I've read, ocellaris are a bit more finicky and less apt to go to a BTA.
I think the primary problem when a clown won't be hosted by anemone has to do with it being an unnatural combo. For instance, ocellaris go to mags like magnets, even when they're tank-bred. I've seen that happen repeatedly. Likewise, percs make a bee-line for mags as well. Generally maroons will be in a BTA before the anemone has a chance to settle in. The list goes on.