Once couples have been admitted and are inside Canada, of course there is the potential for domestic abuse. If that happens, it can come to our attention through the CBSA's Border Watch line. It can come to our attention through CIC's call centre.
In the case of straight domestic abuse within Canada, those cases are referred to the local police. They have the jurisdiction. The cases may ultimately be referred to social services. That's not, strictly speaking, a CBSA concern. If spousal abuse that happens within Canada leads to the wife going to a women's shelter, the CBSA has a very strict policy about entering women's shelters. For example, only female officers are allowed to even approach a women's shelter, and those female officers have sensitivity training.
Of course, if marriage breakdown in the spousal sponsorship program is due to abuse, then the victim is not re-victimized by being sent back to the country of origin, as you're aware.