I've had FiOS for 2 years now, and no RFI. That said, I wouldn't be surprised if there's an issue with the wired ethernet side. Lots of routers/switches are pretty bad with noise radiated from the network cables (common mode) originating from the switching PS wallwart. Here, at least, Verizon supplies an Actiontec router/firewall/appliance that hangs off the ONT, powered by a small switcher wall-wart. (recently replaced by Verizon.. the new wall-wart showed up in the mail with instructions to replace it immediately for sort of vague reasons.. I didn't bother to inquire why).
There are LOTS of variations in installation of these things, by the way. My ONT is in the telco cabinet on the side of the house, and the actiontec is is probably a meter away, as is the power supply for the ONT, all running off a dedicated branch circuit from the panel, which is right next to the the telco cabinet. All the wires are real short, both network and power. The installers told me that other folks in the tract, though, have had them put the ONT on the other side of the garage, and the router at the other end of the house, with many feet of power supply wiring, or network cables separating the boxes. That might account for some of the RFI issues.. Nothing like having the battery and charger 20 feet away from the ONT or routing a UTP network cable from the ONT to the router the length of the house.
I'd start with a stack of 2.4" toroids in 31 mix, and start choking all those cables.