Is this hiring binge because of a whole bunch of new customers who have left Bell and Telus? Possible, but I doubt it. Clearly, these "new" positions will replace existing postions somewhere else in Canada (Montreal, Ottawa, London, Brampton, Toronto, Moncton, Saint-John's or Calgary) or replace third party contracts (Saint-John NB, Kentville, NS, and Montreal).
I'm not sure why there are any call centres left in Toronto. Finding people there who speak English clearly is more and more of a challenge. Labour is cheaper in other parts of Ontario/Canada and long distance bills are essentially nil thanks to voice over IP.
Granted, call centres need a huge labour pool because of their high labour turnover (at least 200% per anum, often many times higher). With three universities and many more colleges, Toronto is in constant supply of recent graduated eager for work. But if these graduates (and lets face it, drop outs) can barely be understood by the average Canadian, I fail to see the point.