If it is TD, I suspect it's a "hot" backup and disaster recovery site for the bank in Toronto. Inside would be rows and rows of a few hundred computer terminals setup to be quickly configured and linked to whichever internal corporate TD network is necessary; banking, insurance, asset management, capital markets, corpoate accounting, etc....
Government regulations--and basic business sense--now requires large banks have these backup work locations for emergencies. They are there for all kinds of situations from power outages, to building fires, to civil disturbances (like the G8 summit/riots), and they locate them near, but not too close, their corporate HQ. The purpose is to have a location for staff who are necessary to maintain minimum required business operations to work at for a period generally from several hours up to several days while their regular work site is not available or accessible. It sees regular use because every different business unit of the bank is likely required to do a live test at least once, and perhaps twice each year where all staff go to that office to work, and then report what challenges or bugs they encountered in the system. If there is something incinerated, it's probably for disposal of documents printed out for wrk use that have client information on them.
RBC has a similar setup at their office complex in Meadowvale where two floors are dedicated to hundreds of desks and computer work stations available to all staff from downtown with only a few hours notice to the local IT team. IIRC they had to use it heavily a few years ago when that hydro vault fire happened down on King Street at Yonge and they were forced to abandon the entire office building there.
They are usually not labelled on the outside for both security purposes and so there is no public confusion that it is an office with a customer service staff open to clients.