I haven't looked at that specifically, but I do have some statistics here from StatsCan on the reasons people retire. I think you asked that question among the others you listed here.
These are 2005 numbers, and they refer to people 55 and older who said they had retired. Only 10% of people retired because of mandatory retirement. The interesting thing is that 24% retired because of personal or family responsibilities and another 23% retired because of personal health; health issues seem to be a big reason that people may be forced to retire, even if they didn't particularly want to.
The other point you made is about women continuing to work because they may not have had enough time, because of family responsibilities, to build up retirement income. That's one of the arguments often put forward in favour of abolishing mandatory retirement: it would allow women to accumulate better pensions. I have to confess I have a serious problem with that, because most women are not in a workplace pension plan, and most women's earnings are too low for them to contribute to RRSPs, so telling them they could go on working and build up more pension income, it seems to me, is not a reasonable thing to do. Fundamentally, it is in fact telling women that if they want a decent income in retirement, they can just go on working.
I think we should address that issue by looking at how our public pension programs deal with women--for example, by looking at the possibility of having a dropout in the Canada Pension Plan and in the Quebec Pension Plan for caregiving for elderly family members, in the same way we do for people who care for children. I think that would be a very important issue and would help older women who are being forced to retire because they have caregiving duties. There are other measures we could take like that to help older women, apart from telling them they can just go on working until they have enough money.