Registering your business was one of the few activities you could do on the Service Ontario site for registering business.
Well, that'll change soon. They've been testing some enhanced features. They allowed some basic corporation registration recently, but now you'll have the opportunity to not only register your OCN (or your BIN), but actually file your annual return through the system instead of via CRA.
Hopefully, updating information for your MBL will be faster now too.
It's not officially launched yet, but you can sign up for updates.