That's what I do instead of Night Service (in most situations). With Night Service, someone has to remember to turn it on and off. I set the A/A to answer in 4 rings. That way gives the receptionist enough time to answer the phone and, (s)he doesn't have to run for the phone or worry about lost calls if away from their desk. Also, you don't have to remember to turn it on at night.
Have the A/A answer Table 1 for Company "A" and Table 2 for Company "B".