Fly bhoy
I was under the same impression - the article released by the Union is not very clearly written.
However Jonny B Good who is involved with the Union has stated on the previous page of this thread that the 2% will be paid upon receipt of a 'yes' vote (though it won't hit pay packets until July as the ballot is on 18th June - why so long I don't know, pension vote was pushed through quicker).
Then any other increment will be backdated once the Aug 09 RPI is known. If the Aug RPI is less than -3.5% than there will be talks about how to make savings elsewhere - which sounds ominous.
As far as I am concerned, this is a pay cut however it is dressed up, with fuel prices recently going up and to do so again in September (after the AUGRPI figure is published). The AUG RPI figure that counts is AUG08.
This is how management have always wanted us to work before.