I would like to point out that Councils in Scotland can only place number limits on Taxis; Private Hire vehicles are unlimited.
Drivers here & in Glasgow don't have to log work, in fact any Councils that do issue such a condition are likely be challenged in Court.
Indeed one of the few that do is Perth Council & they have just had their butt kicked in the High Court in London where a second hand car dealers dispute over licence conditions never went their way
http://www.parliament.the-stationery-of ... erth-1.htm
I wonder if there are still no Enforcement Officers in Glasgow ? I have seen quite a few unlicensed Private Hire cars on the road there & this would explain why they haven't been caught.