I think you are conflating the Flock cameras with other things the police do.

On a flock camera they can only see what the camera sees.

They also put up wifi sniffers (stingray, imsi catcher) that can capture everything that's sent and / or received to mobile hotspots. Essentially an endless mitm attack. They can do that with a court order.

They can only enter your phone with a search warrant. Practically this only happens when the police are already suspicious of you. Technically this can happen to anyone and everyone should keep that in mind.

But no, they cannot look into your cellphone from a flock camera. In fact these cameras are probably quite bad for capturing anything else other than number plates.