honeysingh is right! background checks will include verification (also known as vetting) of all the information you submitted.....criminality, security, testing, employment and etc. this is standard procedure, except for the more complex checks - criminal and terrorism ties - that are handled by CSIS (security check).
as for your credit......no, they will not be checking that. there are strict privacy laws which prevent government agencies from accessing information, unless authorized. i was speaking with CRA the other day, and was told that even they will not disclose information to CIC, unless the person authorizes it directly. this is why you must send the T4 and NOA yourself. in any case, dont worry about your credit!
the only time financial matters become relevant is when there are criminal charges/proceedings involved.