ATC over Major Centres general question

[BC_Scan]

thanks to ADSB im able to see US Mil planes transiting through my province en route Alaska , WA state etc, flying right over Vancouver at higher levels 35k-40k feet
as they approach a major centre do they have to notify ATC , im trying to understand and listen to planes without visible callsigns

 

[AI7PM]

They are under positive control by the ATC centers. In your case, Seattle and Vancouver. Try 125.1 and 134.95 for Seattle. Vancouver 134.4, 125.95, and maybe a few others here. Vancouver (CZVR) (British Columbia) Scanner Frequencies and Radio Frequency Reference

 

[popnokick]

Seattle and RCAG sectors in the area also operate freqs in the MILAIR band. They are listed here -
Seattle (ZSE) Air Route Traffic Control Center Scanner Frequencies and Radio Frequency Reference
In many areas the military aircraft ARTCC / RCAG freqs are paired and simulcast with the VHF civil air freqs.