I would doubt any regulatory agency would approve a 4,200 hour/no calender limit between C-Checks for the L-1011, without approval by Lockheed.
In actual fact, this is incorrect.
The ex- British Airways L1011-200's that were converted by Marshals to freighters had such an approved maintenance program, and it is still in force today.
Additionally, several other operators also have this maintenance program in force now, and yes, I have seen the approval in writing, from the concerned regulatory authorities.
Specific authority from Lockheed is, in these instances, not required.
Lockheed have, more or less, washed their collective hands of the L1011, and quite frankly, no longer appear to be interested...even for an (excessive) fee.
