I totally agree - the "maggot wagon" moniker was made as a joke (although as you rightly say, in years gone by it was probably well justified in some cases). The street food scene has really exploded in the past decade (as has the Food Standards Agency "scores on the doors" inspections). In Leeds the Trinity Kitchen food court fairly regularly rotate the selection of street food vans on offer in their indoor location to keep the food offer "fresh" to guests.There's a vast industry around street food that has accelerated in the last decade or so. I think a lot of the stigma or associations with a bacon bap van in the car park of a B&Q or a layby has vanished, and presumably the "maggot wagon" idea with it. If anything, people seem to gravitate more towards the concept. One of the local kebab houses near my place has recently started turning up at a market with a 'street food' concept and some nice graphics and seem to have reinvented their trade by association. In Towers case, I would now always opt for one of the event street food vans than Burger Kitchen or Pizza & Pasta, if the option is available.
Whilst many on here may not be fans of the Aramark food offer, they do in the main get 4 or 5 food hygiene ratings (it's not hard to get a 5 with properly documented procedures, documented records, stock rotation, food handling, hygiene etc). There is of course the niggling issue of that "blip" report on Chessington where the findings make the Fawlty Towers kitchen look good [think "Basil the Rat" episode].