It also prevents the purveyors of high quality items from featuring RAF subjects without the permission of the owners of the Ninja Turtles trademark. If a model manufacturer wants to produce an accurate model of a Typhoon in 29 Squadron markings, if a small publisher wants to produce a book about the RAF, etc
Only if the MOD has granted the Ninja Turtles exclusive use, which I doubt (if they have then they are truly Muppets
TM and I take it all back).
The model issue is murky but recent experience in the US suggests both the aircraft manufacturer and the MOD could enforce copyrights should they choose to do so. As I understand it a publisher of a book does not need a licence from the MOD to publish pictures of RAF kit with RAF roundels on it, any more than Airforces Monthly or the Daily Mail does as copyright in this case rests with the photographer as creator of the image. If they want to incorporate the roundel into the design of the book/magazine, that's different.
Railway modelling is exactly the same (it started off as a modelling question so why not). Bachmann and Heiljan both produce models of Virgin Trains Class 57s, for which both hold a licence from Virgin to reproduce the trademarked livery. However, only one of them (I forget which) has the "Thunderbirds" nameplates attached as the other couldn't (or wouldn't) obtain a licence from whoever Gerry Anderson sold the rights to.
Edit - Definitive (?) answer here:
http://www.mod.uk/dpa/project_servic..._and_logos.htm. Apparently Airfix already hold a licence, the MOD are now going after smaller manufacturers. If your reproduction of trademarked designs is not for commercial gain the licence is free. Totally agree that there must surely be more important things for them to do though.