I'm not sure how HTA 172 relates but the law looks at the danger to the public and determines the risk regardless of whether the property is private or public.
The HTA applies, or it doesn't apply - there is no in between.
This was hashed out in Ontario during the infamous Tim Hortons texting ticket story last December. People here in Ontario were quick to ask if the same law potentially applied here in Ontario...and the result was basically the same as in the story linked here:
“They can only be charged if they are on a highway, which includes the sidewalk and driveway into the establishment,” says Const. Clint Stibbe, with Toronto police traffic services. “The drive-thru, if on private property, is not included because the highway ends at the edge of the sidewalk closest to the establishment.”
That’s because Ontario’s Highway Traffic Act (HTA) doesn’t apply on private property, like drive-thrus or shopping centre parking lots.
If the HTA doesn't apply for cellphone tickets on private property, it doesn't magically apply for anything else either...including 172.
Of course that wouldn't stop a LEO from issuing a ticket of course, but I see no way it would stand up in court.
Even amusement park rides have to pass some inspection criteria.
Apples and oranges.