I think the way it works is for obtaining warrants on the weekend and after business hours is that one of the assistant chief crown prosecutors is on call for weekend warrants and arrest decisions (assistant chief crown prosecutors have this weekend role on rotation). A Judge is probably on rotation for those decisions as well. With the probable cause of a vehicle matching the one at the crime scene, a warrant would have been issued for the vehicle, the property, the house, and probably for any businesses associated with the owner of the vehicle.
I would expect that all departments connected with homicide investigations will be involved with the search.