Yes, actually the CRTC imposed Bell to apply this to its own customer first. The way I understand it:
A. Bell customers:
Customer uses much bandwidth. Bell pays for internet bandwidth and gets paid by customer.
B. Wholesale service:
Customer uses much bandwidth. ISP pays for internet bandwidth AND pays Bell for usage, then ISP gets paid by customer.
Despite the fact that *everyone else* involved in the process were against this, the CRTC agreed mostly because it was claimed there's the same practices in Cable wholesale. The difference, though, is that DSL is dedicated access, and once the infrastructure is paid for (trough the base fee) there is nearly no costs to additional bandwidth besides the Internet bandwidth which is already paid by the ISP. Cable, on the other hand, is a shared medium with limited bandwidth, and the more customers use ut, the more has to be spent on upgrading the infrastructure to prevent congestion on the cable segments.
This scheme will hurt small ISPs which will have to impose limits, while it will allow Bell to make more profits and possibly cut its own prices at the same time.