I'm posting this message of thanks to the helpful folks -- especially the service advisor -- at Yonge North Mitsubishi in Richmond Hill, Ontario.
I picked up my used Mirage from the Toyota dealer next door where it had recently been traded in. On a whim, I dropped in to the Mitsubishi service department just to see if it's possible to get a print-out of the car's service history from any Mitsu dealer (I assumed they'd be networked and I could do it closer to home).
Lucky for me, Grace was at the service desk, and she set me straight:
1) The dealers aren't networked - I could only get service history info from the location that did the service;
2) Extra-lucky for me: a search of the VIN showed my Mirage was serviced at that very dealership!
Grace very helpfully printed out the car's maintenance summary, going back to day one. And she went above the call of duty, since she had to figure out a way to do it that wouldn't identify the previous owner (whose contact info was in the service records).
She could have just said "sorry, can't do it". But after a minute or 2 of working on the computer, she said "aha!" and fired up the printer.
With that kind of service, I wouldn't hesitate to send any Mitsubishi owner to her dealership. Thanks, Grace!