Looking at your pictures along with satellite and street view imagery, I'd say that these are not the kind of camp cottages we talk about from 1906. The size and shape just don't match the standard cottages that were built in SF parks. That's not to say that they weren't built in 1906 or used by refugees in Oakland. The idea that these could have been transported across the bay seems very unlikely also. It's possible you could find Oakland property records that verify the claims, but these don't really pass the sniff test.