According to the product information for Bio-Mop Plus you should get some immediate cleaning from solvents in the formulation, as well as long-term cleaning due to the action of the bacteria. When you apply it to a floor surface it then flows into floor drains, and now works to eat away the buildup of organic sludge in that setting, discouraging the presence and breeding of drain flies and phorid flies. It would be of some importance to keep in mind that this product is not specifically registered by EPA as a pesticide, and therefore the Label cannot make claims to assist with fly management. It only can claim to remove organic materials and provide cleaning. 

Depending on what your fly problem is at this restaurant this kind of application may or may not be helpful. If it is small flies that could be breeding in the organic materials then certainly it will give immediate results. If the problem is, as is so common, houseflies drawn to that outdoor eating area, then cleaning the floors may not be as much help as you would like. Definitely dirty floors are going to contribute to the overall attraction of flies, but houseflies are breeding in very different areas and will come to food service establishments because of the odors of food or garbage. You might do well to evaluate the overall setting for any and all sanitation issues. This includes the waste stream inside and outside the restaurant. Is garbage inside disposed of properly and removed from the inside on a daily basis. Are the garbage receptacles inside kept clean? Is the dumpster area outside clean (this would be another good area to spray with Bio-Mop Plus) and the receptacles clean and with tight fitting lids in place?

The use of baits outdoors would be excellent, including spray on / paint on baits on exterior walls using products like Maxforce Spot-on. Trying to keep the numbers of houseflies down to a tolerable level requires the use of as many tools as possible, so you could also install fly traps around the dumpsters, window glue traps inside, UV light traps inside and possibly under cover for the outdoor patio if it is darkened enough. Each tool on its own is unlikely to control the problem sufficiently, but putting them all together, with each one capturing or killing more flies, the overall result gets to a decent level. The customer still needs to understand, though, that he cannot expect flies outdoors to get to zero. You cannot control the presence of flies around the exterior environment, and more are always going to fly to this place to investigate the great odors they detect.