I don't trust them. I have green striped and red mushrooms. They both coexist together, but the greens have a truce with brown button palys, they both tolerate being close, but I think the mushrooms make the palys close more. They will cover GSP and make them close.
Softies like nephia and colt seem to get along, but those usually grow above the mushrooms.
I don't dare have them get established in zoa country. I had one pop up in some midnight suns which are still alive, but I want to get rid of it.
I planted a small frag of hammer between some mushrooms and palys, no one is really winning, the palys may be closing up more though, due to the hammer.