Hi
With most airlines, the FPL would usually be 'sent' to the FMS and checked then accepted by the crews. Some operators (smaller operators and some biz-jet operators) will manually enter data. NAT tracks would not be in any database due to the fact that they change daily due to the fact that the weather changes - namely the jetstream.
So, in a word, yes, it's for manual entry of waypoints in AIRINC 424 format, not just for flying the tracks or random routes either, but mostly this is where it would be utilised.
More gen for you:
RAC - 11.0 NORTH ATLANTIC OPERATIONS - Transport Canada
Section 11.4 of the above should fill the gaps.