Collins/ARINC is used for oceanic HF radio. They run "San Francisco Radio" and "New York Radio" specifically, which are the HF radio operators that relay oceanic messages to ATC.

(They also own a small number of private VHF stations for relaying company messages to air carrier operations domestically, but these aren't used for ATC purposes.)

Otherwise, the VHF radio links are operated directly by FAA TechOps.

L3Harris owns the telecommunications backhaul between facilities.