The point's moot really. It's about the demarc point. Verizon owns the fiber and the ONT up to the designated demarc which is defined as the "customer side" of the ONT (i.e. the ethernet, coax, and phone ports).
The Ubiquti ONTs will not work either. The OLTs which is what the ONT connects to back at the central office are vendor specific. Verizon uses both BPON and GPON ONTs. Tellabs and Arris(now Commscope) and Alcatel(now Nokia). Each vendor use different OLTs. Fox example you can't mix Arris and Nokia GPON ONTs on the same PON. Verizon would have to install Ubiquiti OLTs at their central office for that ONT to work.