I am not sure if there are specific requirements for therapy animals in Canada. I know that there are groups that visit seniors homes, hospitals and other places and they generally will certify the animals on their own. Training can vary from group to group, some may require specific training while others go for the temperament and basic training.
I think one big thing is insurance, the person bringing the animal needs some protection if something were to happen.
If she works for the agency and they are her personal rabbits, she might want to talk with whoever runs the agency about it. It can give her a base line on what she needs to do. If she does need some sort of certification, then she could try contacting a local pet therapy group and see if they can help.
Keeping in mind that the rabbits would be therapy rabbits and not service animals. Service animals receive lots of training to help someone manage a disability while therapy animals provide comfort and a friendly face. Service animals can go anywhere with their handler, specifically areas that pets are not usually allowed. Therapy animals do get to go to some areas that pets are not allowed, but they have no legal protection to go, if a hospital or seniors home said they can't come, then that means the animals can't go in.
With the hopping club, we do go to some seniors homes and the Children's Hospital. A few of the seniors homes have has us come just to visit with the residents and after a hopping demo we do take the rabbits around to visit. At the Children's Hospital, we do a demo but are not allowed to let the kids touch the rabbits (mostly for health reasons). It is really up to the organization we visit and we do have to respect that.
The seniors homes are booked by each centre, but most of part of the same group.
Another thing to consider is where the agency is located. I used to do some therapy and would bring my dog. The place moved to a new location and pets were not allowed anymore due to the ventilation system. So in this situation, a service dog would be allowed, but a therapy dog would not.