Re: Canada Tax when only spent 3 months here
JB0591 is correct. This time next year you file a 2012 tax return but you only include your income from 01/01/2012 up to the day you leave Canada.
BTW you are not stiffed on your RRSP withdrawal. You deducted your contributions from your taxable income when you made them. Now you have to add them back in. You have still managed to defer tax, which is the next best thing to saving it.
Any reference to tax above is for general interest only and is not intended as professional advice.