Hi Nathan,
I don't think it's productive to discuss the similarities/differences between specific operating rules or train protection systems in the US and Canada on-list. Clearly, we have differing views on what does or doesn't qualify as being directly observable on the ground, but that's not something I think we need to reconcile for reasons I'll lay out.
I agree with your and Maarten's assessments that there is immense value in including non-directly-observable information in ORM, no matter where we draw the line. As wayside infrastructure starts to disappear in favour of radio communication, I think the "on-the-ground" rule/principle will become increasingly difficult to adhere to.
My sticking point with your original proposal is including operating rules in the train protection systems tagging schema. I'm not necessarily trying to nitpick anything else; I'm more thinking out loud about where more description (good!) would fit in (purely from a user's perspective). On this point though, I have to agree with Michael: ETCS, LZB, AWS/TPWS, ACSES, PTC, etc. are clearly distinct from OCS, CTC, TWC, cautionary limits, etc. and IMO should have a distinct tagging schema.
I would gladly support a proposal to add tagging for operational rules *iff* it can be done in a sensible way that doesn't conflate these two concepts.
I'll keep monitoring the discussion.
Cheers, --Tyson