Originally Posted by Ross182
...its still a VFR flight (even is in IMC)
An interesting, but not very helpful approach.
Different States have different rules about IFR flight outside controlled airspace. In some, it is simply not permitted, in others it is permitted in accordance with Annex 2 IFR or a local version thereof, in at least one (being the UK) in some circumstances you can fly IFR outside CAS and receive an air traffic control service in all but name. I think that last bit is still true but am happy to be corrected by someone currently operational in the UK.
But to answer the original question, in most situations an IFR clearance can only be issued to flights whilst inside CAS. Using the vanilla, ICAO rules, what happens outside CAS, by definition, is not under the control of ATC. If a VFR flight finds itself unable to maintain VMC and looks to join the ATC system I would expect a procedural clearance to be issued to enable the aircraft to join CAS, at the CAS boundary, under IFR climbing to the lowest available level (moving other aircraft out of the way, if necessary). How the aircraft gets to the base of the CAS is the pilot's responsibility, and whilst it may be quite obvious that the pilot will have to breaks some rules to do so, the controller is a controller, not a policeman.
If the controller is aware of obstacles or other hazards that the pilot may encounter on the way to the base of CAS, he/she will, ideally, provide all information that they can to avoid the pilot failing to have the opportunity to take advantage of the IFR clearance. Again, rules differ on how much a controller can help a pilot in this situation.
My last thought on the topic is that the art of issuing procedural clearances appears to be dying, so maybe my answer is getting outdated. As ever, I'm happy to be corrected by someone doing the job today.