Once MTO or Police confiscate plates, those plates cannot be returned. You must go to the ministry and get new plates for the vehicle. Summons are summons because they have no set fine, based on severity, repeat offenders, etc, the fine will vary.
You were charged with:
84. (1) No person shall drive or operate or permit the driving or operation upon a highway of a vehicle, a street car or vehicles that in combination are in a dangerous or unsafe condition.
75. (1) Every motor vehicle or motor assisted bicycle shall be equipped with a muffler in good working order and in constant operation to prevent excessive or unusual noise and excessive smoke, and no person shall use a muffler cut-out, straight exhaust, gutted muffler, hollywood muffler, by-pass or similar device upon a motor vehicle or motor assisted bicycle. R.S.O. 1990, c. H.8, s. 75 (1).
The Fines for these would be:
84 (1): a fine of not less than $400 and not more than $20,000. 1996, c. 20, s. 19.
75 (1): Can't find any information on this (Ontario Courts Website says Revoked), but I'm assuming it's the standard Set:$85 Total:$110.