The "current administration", as you put it, doesn't make the decision. Planning applications are decided by the Planning Committee, which consists of 12 councillors - 5 Greens, 4 Conservatives, 3 Labour. The Greens hold the position of Chair, the Conservatives the Deputy Chair. Decisions of the Planning Committee cannot be overturned by the Administration.
His point was the Greens are in the driving seat on a decision about expansion... and that's still the case isn't it - they have 5 councillors?