Last I checked BIP110 will have a mandatory signaling window in August, so if miners don’t signal, BIP110 nodes will in fact fork themselves off the network.
Your scenario could still happen if min...
(To be precise I think the 1109th signaling block within a difficulty window should be rejected, as that would bring it over the 55%-threshold, and makes for a relatively clean split between the BIP110 chain and the original chain.)