This press-clip from brazilian Flap magazine (Issue 226, Feb. 1991) states that VASP leased TAP L-1011's to increase their capacity in the RIO-SSA-RIO route, taking advantage of the long parking time that these aircraft had at GIG airport: the flight from Lisboa arrived early in the morning and the aircraft wouldn't make its return until evening.
However it seems the real deal was a little bit different. TAP used to make a stop at SSA (Salvador) in their route to RIO two times a week. So VASP bought a block of 60 economy seats on the legs between SSA/RIO/SSA. VASP's marketing sold these seats with the following slogan in portuguese 'RIO - Salvador e Salvador - RIO, pela VASP com sotaque português' which means 'Rio-Salvador and Salvador-Rio, fly VASP with portuguese accent'.
This press clip was found via AeroFórum.