I'm not a lawyer but I do have two of them in the family and I have stayed at a Holiday Inn Express.
If this had been in the US and assuming there was enough probable cause to pull him over for exhaust noise in the first place, then there certainly was enough probable cause to look under the car and take pictures.
Besides, unlike the US, probable cause is not a requirement for traffic stops in Canada. They treat driving as a privilege not a right (actually it's a privilege in the US as well but not to the same extent) so a driver is expected to put up with traffic stops for everyone's "safety". That's why they can do random drunk driving checkpoints that would be impossible (lack of probable cause) in the States.