There are 55,000 workers in downtown London so it's not inconsequential. The other 3 big ones are Western, Fanshawe, and LHSC which is the biggest hospital in SWO.
London, more than any other city in Southern Ontario has the ability to support commuter rail. London is very centrally located with excellent rail connections in every direction. What's more they all go right downtown to the VIA station making them very convenient and just a single block from the new downtown bus loop which gives them access to every downtown bus in the city including the new BRT and current express buses.
Added to this, London, unlike every other city in Ontario, doesn't have an urban freeway. Even the regular routes are overwhelmed and disconnected. Anyone who has ever tried to get a cross London in rush hour knows that it could try the patience of a saint. It m not only makes driving hell but conversely make commuter rail potentially much faster. As an example the slow, unreliable VIA train takes just 23 minutes to downtown London from Strathroy with 16,000 and a big commuter town. In rush hour it's at least 45 minutes and even at 3:00AM on a Sunday morning it would still take you at least 25.