Ex-scooter rider here chiming in. I speak from personal experience only so take it with a grain of salt and for all I know, I may be very wrong. Your mileage may vary.
49cc scooters: You can safely take the Oak Street Bridge taking the Bridgeport exits. Failing to do so could put you into a dangerous, if not, life threatening and stupid situation. Basically, the first and last exits on the Richmond side. The speed limit there is I believe 50 or 60km/h. You should be able to keep up with the flow of traffic, especially during rush hour. Always stay in the right lane.
Arthur Laing Bridge - same situation applies.
Knight Street Bridge - If you want to play by the rule book, you are technically not allowed on it because the max speed limit is I think 80km/h? But legally you should be maintaining 60km/h and/or keep up with flow of traffic. Having said that, a 49cc scooter should be able to maintain speed during rush hour gridlock traffic. Again, always stay in the right lane and enter/exit only from the Bridgeport exits. Any further - you are fucked and asking for a death wish.
Lions Gate - you should be fine during rush hour. Might get some angry cagers hassling you during off-peak hours but whatever. You are allowed on it as long as you maintain minimum speed.
Second Narrows Bridge & Massey Tunnel - LOL! If you want to die, sure. Go for it. Otherwise, you're not allowed on it whatsoever with a 49cc scooter.
Alex Fraser - Fuck Surrey. But personally, I don't know. Never rode on it on a scooter and don't care to. Sorry. Jokes aside, I think the incline on Alex Fraser is just too much for a 49cc scooter to maintain any kind of speed and getting on or off it is a real hazard so, I wouldn't even bother unless you feel like dying.
That's all I can think of. #YOLO. Good luck and ride safe.