I went to the bunker the other day, which takes place early in the morning for me, around 5am, so likely around 9am cali time?
Anyway, there was about an hour of pvp in the lead up with plenty of RG on. only 4 of those RG showed up to bunker, 1 of which was an FK alt.
Find a way to encourage them to show up, it's all you can really do.