No good answers
Two years ago I would have said TC and NAV Canada won't be able to agree on anything, so I installed a GNX375 and love it - ADSB, UAT all nicely integrated in one box. I put the antenna well towards the tail to give the best upwards visibility, and crossing my fingers that a TSO compliant installation with antenna on the bottom, and passing the satellite test will meet the requirements.
I'm redoing another panel and we have the reg update - but I'm not sure if we have more clarity - other than it looks like TC and NAV Canada are agreeing.
https://www.navcanada.ca/en/aiceng202326.pdf
https://tc.canada.ca/en/corporate-services/acts-regulations/list-regulations/canadian-aviation-regulations-sor-96-433/standards/airworthiness-chapter-551-aircraft-equipment-installation-canadian-aviation-regulations-cars#551_103
The reg specifies generically that performance requirements will be guiding but I've not seen good guidance on how to test both for ground based and satellite based for a given installation, and we have of reports of installations having challenges getting enough hits on the satellites.
I think you are safe if you spend a tonne of money on a dual antenna setup, or use a tail beacon (or other TSOed device with an antenna that points out and down) based on the AC but I'm not happy with the trade off on integration with tail beacon or the dollars of dual antenna. I figure worst case in 3-5 years I may have to sell my 375 to a happy US customer and do something else using whatever options are available then.
Lots of things can happen between now and then. Someone may create an antenna that generically points up and down, NAV Canada may decide they need more time to put more satellites, NAV Canada may decide to put in ground stations, tailbeacon may integrate to Garmin, not to mention whatever new avionics show up at OSH over those years.
Updating an existing panel to ADS-B out, tailbeacon would be the easy choice for me - fixes flying to the US and Canada at the same time and use something else for IN (I have a GDL52 that I move between planes for XM and ADS that covers that), but for trying to design a new 10 year panel with no add-on boxes, I don't think there are any good answers yet.
Still have my fingers crossed that my current setup will be enough for Class C. We will see.
Derek
edit: There is also
https://tc.canada.ca/sites/default/files/2022-05/AC_500-029_ISSUE_01.pdf where TC essentially says you have to meet the NAV Canada requirements, whatever they may be - if you are certifying a new device/plane. "To
receive space-based ADS-B surveillance services, the applicant must ensure that the installation
meets the performance standards required by the air navigation service provider.
"