If they were removed due to nonverification with the OC and they later do verify, yes, they can come back. But you would need to be notified by the CRA within 5 days of their reinsertion,
How old were they?
Or if the collection is sold to another CA, it can show back up that way. Are the debts paid now?
When you file a dispute through the CRA the creditor has 30 days to respond. If not they are deleted. If, at a later time, anyone can verify the debts as being valid, they can be reinserted. The same creditor or another CA would have to go through the verification process and the CRA would need to certify they are valid.
Thanks all. I thought I had read somewhere in the threads that this could happen, but I couldn't recall accurately. The original debt is a government fine rather than money owed to a credit issuer so it is unliklely to ever be transferred (the local gov has a lenghty contract with a particular CA). I'm still glad its not currently reporting as I work to pay off each fine although I wish there was an option for settlement.