The province owns the plates, they're not yours to sell, give away or transfer in any way... or take to Australia
Pretty sure you could transfer a personalized plate, but it would take a long time.
In Ontario, like other places, you register a vehicle with a plate from the year the vehicle was manufactured (remember we got plates with no dates in '80s, so it's all old stuff). So you have a '73 bike, you can go find a 1973 Ontario motorcycle plate at a flea market. You send that plate to MOT headquarters and they do what ever they do with it (it has to be in decent, read EXCELLENT, condition, not listed as stolen, the number isn't a duplicate....) and if it's acceptable, you get a letter that says the plate is property of The Province of Ontario (again), it also says you owe about $350 and you get to use the plate... and it takes a year... or two. The whole process is in the "personal" plates program.
... so they're selling you a concession for the $350, and you could sell/transfer that concession, And I betcha it would take a lot of time and arguing with MOT... but doable.
Yeah I've got a stack of old un renewed Ontario plates too, but I don't own them.