As far as collisions; I am not sure. I know that US Space Command monitors low earth orbit and if you are the operator of an asset which is in the path of another asset they will contact both parties to organize a response. Usually this requires one or more assets being moved. Whether or not the operator of the asset is cooperative with US Space Command is entirely deterministic on the relationship of the operator to US Space Command. Russian military satellite operators probably won't answer that phone call.

But that is not the only threat they pose. If you see the links I posted, the satellites are so low, so reflective, and so numerous that they impact ground based astronomy of all kinds. From the reflection of the sun off their metal components to the radio interference they emit; these satellite's are a menace to the scientific community.

I'm sure the logistical challenges they provide to operators trying to launch new spacecraft is significant as well. And there are other organizations from other countries building similar constellations in low-earth orbit. These are all disjointed teams with little to no knowledge of each others existence, let alone communication with each other. We need a regulatory body with the authority to gather all vested parties and hash out some rules that work for everyone. We needed this done BEFORE SpaceX shipped a portion of the world's precious metals into low earth orbit. But that didn't happen. And universities are paying the price while SpaceX turns profit in space.