BRU and AMS have Level2/3 systems. AMS in particular installed transponders in all their manoeuvring area vehicles and came up with a number of 250 installations. I thought that ridiculous, until I totted up the number we'd need at LGW and it comes out pretty much of that order. Amazing! That's just essential vehicles on the mauoeuvring area, NOT the Apron, so deosn't include catering trucks, baggage vehicles etc. Only Fire Appliances, Works vehicles, Operations vehicles, Snow kit and so on.
Labelling with current single SMR systems isn't very reliable, with labels often re-attaching themeselves to other fixtures & fittings. Multi-lateration isn't the whole answer, either.
Personally, I'd rather go for a GPS-based position-reporting system and cameras to read a/c registrations as they come off the runway. Fortunately, I'm only an interested bystander!
TOO