Forget timelines, which will be a whole other problem, but it is easy to see how there could be discussion and movement.
The seemingly intransigent issue is the single market and freedom of movement. Theresa May has taken the Brexit vote as the nation’s unwavering demand for some form of immigration control. The EU’s chief negotiator stated yesterday that access to the single market depended on adherence to its four freedoms, one of which is freedom of movement, He said it was indivisible.
Now other countries who are not members of the EU do have access to the single market – Norway has full access, and Switzerland has a more limited access. Both of those countries make a contribution to the EU’s budget. So the obvious suggestion would be that if Britain was prepared to make a suitable contribution then it too could have full or partial access to the single market.
But both Norway and Switzerland accept freedom of movement. The only real difference within alternative EU relationship models is membership of the customs union. Broadly speaking those countries and organisations who have trade agreements with the EU but do not have access to the single market, do not make a contribution and do not accept freedom of movement face tariffs. If the EU is prepared to move – for the first time – on freedom of movement, it will almost certainly come at a high price.