Hi,
As I mentioned, as per CIC:
As a post-secondary student
You may change your school, program and/or field of study without applying for a new study permit. You do not need to apply for a change to the condition of your study permit, either. You may continue to use your study permit as long as it is valid.
If you are changing your level of study (e.g., bachelor's to master's), you do not need to apply for a change to the condition of your study permit, either.
(http://www.cic.gc.ca/english/helpcentre/answer.asp?q=487&t=15)
If your study permit is granted, you will actually be issued a TRV on your passport by the CHC. Once you land in Canada, at the airport entry point, customs & immigration will check your documents and issue you the actual study permit (with name of the 1st University on the study permit for which your visa was granted). There is no work permit involved, unless your course has a co-op option, which is usually granted right there with your study permit.
Then, simply go to the 1st university, show valid offer letter of the 2nd university... before the withdrawal deadline... cancel admission from the 1st university, get fee refund less administrative/cancel charges (usually transferred directly to the new educational institute or transferred to your bank account) and join the 2nd university of your choice. NO need to make any sought of changes to study permit or any need to notify CIC. All this, provided you still have valid admission status in the 2nd university of your choice and that 2nd university is NOT in the province of Quebec, where you will need to apply for extra CAQ (Quebec Acceptance certificate).
***All opinions expressed are purely personal, and pieces of information mentioned are to the best of my knowledge... You should consult other sources too.