Many seem to. Projects like Seedvault seem semi-collaborative and used across several ROMs, Lineage is a starting point for a lot of ROMs, and there was an attempted AOSPAlliance. From what I’ve heard, some of the ROMs have pushed changes upstream to Lineage as well.
Without pointing fingers, it seems like most projects seem/seemed to get decently along. You can try to dig into the history of things like AOSP alliance to try and see where potential issues may have come up, I definitely have onions on the matter on the people who tend to be problematic 