It seems to be a bit of a lottery and down to individual tax inspectors/districts.
A few years ago I met a gentleman whose company had a small aircraft. He used it for business purposes and some pleasure flying. The inspector decided that he would do the apportionment on a daily basis - allowing the days on which he flew for business but charging him for all other days since the aircraft was available to him personally on those days.............
Funnily enough he sold the business, the aircraft and his house - taking his money and talent back to Canada!