A person can only have one PPR at any given time.
The relevant date for 2011 is 31st March.
If it is established that a person owns (has a property registered in his/her name) that is not their PPR, then they are liable to the tax.
Therefore the only problem is to establish a person's PPR on 31st March, and take it from there.
If there is any doubt about a persons PPR, the people to establish the facts are the relevant local authority.
No amount of speculation here or elsewhere will change that.