A collection agency is able to post an item to the credit bureau (that is, Trans Union Services and/or Equifax Canada), as long as there is reasonable belief that the debt is true valid.
If the agency has a social insurance number and/or date of birth, this makes the likelihood of matching it to the consumers' credit bureau much higher, but they do not need that information. As long as they can provide a last known address with a postal code, the credit bureau will make an attempt to match it to the correct file.
In many cases, there is the issue of "garbage-in-garbage-out", where various creditors might report different information (married names vs. maiden names, misspelled addresses, etc), causing a consumer to have more than one credit rating. However, if the credit bureau discovers such a thing, they will make every effort to merge the records together (and mark aliases, AKA, etc).
Everyone should get a copy of their credit bureau at least once a year to see what is on there.
Trans Union Services 1-800-663-9980
Equifax Canada 1-800-937-4093