DI Ross has been "on the force" for 14 years as revealed in flashback (where he looks exactly the same) and conversation with DS Reid. However, he appears to have started his police career as a Detective and not a PC. Unless he means he has been a member of CID for 14 years and was a PC before that it as is highly unlikely he would start his career as a Detective.
The upstairs area of the police station (which is supposed to be in Maryhill) is shown to have views of George Square etc in Glasgow City Centre which would not be possible to see from the real Maryhill. The filming location of the station entrance as seen in a lot of the 21st Century Taggart episodes is actually just off the real George Square.