Yes, it is an option.
From recollection it holds about 8.5 tonnes of fuel (about the same as the wing on a 737-200!).
For take off the engines are fed by their respective wing tanks, shortly after take off fuel is fed to all engines from the centre wing tank. Once sufficient fuel has been used from the CWT the Stab tank fuel is pumped forwards into the CWT. There are 2 pumps, and if for some reason you can't pump it all forward, there are some very severe consequences due to Cof G implications - you cannot use CWT fuel nor jettison fuel. The wings hold 110 tonnes, the CWT 55 tonnes. You must land with minimum 15 tonnes in inboard wing tanks to maintain CofG limits. This could mean you land with, in the worst case, 55 tonnes (CWT + Stab tank) + 15 (or more) tonnes (wings). This is quite likely to mean landing above max weight by about 30 tonnes, with a Vref of about 170 kts.
Normally it is used only when you load over about 125 tonnes of fuel for the flight (about10.5 hrs with reserves) and can be used for trim reasons. Obviously you don't NEED to put any in until the wings and CWT are full.