The Garage's Cameras would have seen nothing, the Agent having used a cloaking device to get through and the cameras used by this particular garage seem to be rather cheap so they can't pick up the slight tells of an Ocearan Cloaking Device (tiny black dots and a slight distortion) likely the mechanic felt that simply having cameras would be enough to deter
The OIF Is confident that their bug in the wrench will not be detected as they believe Torchwood would be too cautious to want to search each tool in the building as that would take a long time and increase the odds of the Agent being detected. A torchwood field agent is nothing to underestimate but even so, there are limits to the capabilities of a single lone individual.
A city patrol, unaware of the operation at all, is in the area. The patrol is made up of 3 Robotic Infantry and 1 Human Patrol leader. All armed with patrol rifles and pistols which have two barrels -- one for lethal force and one for deploying a capacitor bullet designed to embed itself into a target a very small depth and electrocute it. The leader's capacitor bullets being a bit different, not designed to embed in a target but rather just hit them and discharge everything all at once to blow the target off their feet and make it difficult for the target to run or attack.