Not a joke, a typo - it's "Spin v.s. Trust" - http://twitter.com/alphagov/status/68322599503011840
(@alphagov turned round an answer to my question in less than a minute!)
Can't help but feel that they opted for spin over trust in that reply, I can't see how they meant that to be a 'v'.
My guess, and obviously I could be wrong, is that it was an internal joke, but not meant to be for public consumption for fear that people wouldn't get it and would criticise them for it.
Although from a government that seriously thought they could sell off all the forests without anyone getting annoyed, I am unwilling to assume anything.