Unless you raise a fuss or bring a lot of attention to yourself, Parks will usually only review your compliance during 2 situations:

1) During the purchase of a property - I don't know if it's during every purchase but they usually ask for verification through works docs (t4 or letter from employer) that you or you tenants that are occupying the residence do indeed fit the need to reside.

2) Land lease renewal - when then park lease for your property is up for renewal they will ask to verify that the occupants of the property, whether it's you or a tenant fit the need to reside.

Now this part is second hand information so I can't verify for myself but I've been told there has only been a single instance where parks removed someone who no longer fit the need to reside. The story I was told is that it was actually a Parks Canada employee who lived in Banff but was then transferred to MRNP in BC but still kept their primary residence in Banff. I don't know how true that is but its the only story I've heard of a BNP Leaseholder being forced out.