Flight plans are not copied to any Class D units enroute, either.
This got me thinking though, with the advent of AFPEx whenever I file a FP I address it to anyone near my route of flight. So if flying to the Channel Islands, Bournemouth and Southampton are on my list of addressees (as I can use EGHH as an alternate). Now if one were flying IFR OCAS in the UK, say Bournemouth to Newcastle, could one address the FP to everyone on route so then they would know you are there, or doesn't it work like that?