It is not clear to me that there is a ceiling on how much a long-term disability attorney can charge in Canada, but it is clear that you do not pay unless and until you win. So the out-of-pocket outlay is zero. See, e.g., this link

In other words, in Canada, as in the US, such lawyers represent clients on a contingency basis and there is nothing to lose for engaging them. There is much more than just filing the forms correctly when you are seeking disability insurance.