While the TAFL may not show you any such frequencies due to its policy of not containing 'sensitive' or 'protected' information, the agency you're looking for in Canada's case is called the Canadian Border Services Agency, or CBSA. I don't browse the Ontario database often enough to know if anyone's logged CBSA freqs for your area. You might also want to check the database sections for the state that you'd be in if you crossed over the border.
You might want to see if you can get the MPSCS system. http://www.radioreference.com/modules.php?name=RR&sid=100
The rail crossings near Sarnia get busy at times. Look under Federal Government Talkgroups. I've heard TG 2380 CANUS C.B.S.A./U.S.B.P. - Common, a few times plus the USBP TG's
Interesting thing is that CBSA (spelled out fully) shows multiple licences
in TAFL, but not always for the area of use. For example, Ottawa is not
listed on 410.4625 but it shows up in some other location(s). Plugging
in all the frequencies should reveal at least some active. Also, 410.4375
seems to be active in the Kingston area. I also see some simplex in the
415MHz range (415.6125).
How about Windsor / Detroit Bridge or Tunnel ? Would that also be under CBSA ? or Customs ? I live within eyesight of the bridge and i often see the white pick-ups with lights on top but never see any marked /unmarked police vehicles just windsor police parked in the duty free... thanks GrassHutt