(
disclaimer 
)
Assuming this policy is official.........
I think this possibility is exactly why Disney WILL enforce the rule. If they don't, the ensuing problem will be much worse than it is at present; I'm sure Disney realizes this. Working out the specifics may be what took them so long to enact the new policy in the first place.
I don't pretend to know any inside Disney information (I wish!

) but I'm certain that they would have researched the subject thoroughly before jumping into a controversial policy. They obviously feel that they can/will enforce the policy and that the percentage of people who will be unhappy is smaller than the percentage who will be ecstatic. (I believe that has been well-demonstrated in this thread....)
As a side note.....charging the owner for smoking violations would also affect the commercial renting market....a win/win for Disney?