I haven't read all of the responses, but if the owners did not give them notice in writing that they wanted them to move out before the end of the lease, then I think it technically still falls under the 'breaking a lease' rules. Why don't you contact the Residential Tenancies Tribunal for some advice? They are usually pretty good about coming down on the side of a tennnant.

Have your parents discussed this with the owner, btw. Because the owner can simply notify the RE agent that they are happy for the lease to be broken with no penalty.