The only ones I ever saw around the place was the one who used to tool around in an expensive 4WD vehicle, "inspecting" the runway while travelling down it at 80 mph.......A Vauxhall Corsa would have done the job equally well and much more economically so this just typifies the slack, wasteful bunch that was WMIA.
Now, in the good old days, there were only 13 of us plus 5 ATSAs (4 of the 5 ATSAs plus me all had A/G licences which were used during overnight callouts at the weekend), and we had a knackered old ex-CCC Astra van in a lovely shade of yellow, shame it kept breaking down on the runways and taxiways, oh, and couldn't be used for bird scaring off the hardstanding. As for the speed, once you are used to your runway, with experience, you can run down it an most speeds and still be able to pick up on anything unusual.
If they had an "expensive 4WD vehicle", then it's probably because someone bought it. You use the equipment available.