Peter, an IFR clearance in the US will always include 'expect {insert final altitude here} in one zero minutes'. If contact is lost then 10 mins after airborne everyone expects you to climb to that level. If terrain is an issue at some point enroute then you are expected to climb to an appropriate cruising level above the LSALT before the relevent route segment if the LSALT is higher than the cleared altitude.
Departing into IMC from a non-controlled field that's OCTA ie outside 'E', then you can get a clearance with a 'clearance void' time from a controller. The clearance usually specifies a heading and initial altitude. Many places without VHF ATC comms have an on the ground Radio-to-phone frequency that is activated with a few transmissions. It direct-dials to the local ATC (or possibly Flight Service if an ATC phone isn't possible) so you can obtain a clearance. You can also phone for a clearance if need be although, weather permitting, I usually prefer to depart VFR and get my IFR clearance once airborne.
IFR OCTA isn't a big deal - it's common in Oz, for example.
Last edited by Tinstaafl; 3rd Jul 2012 at 17:39.