I think everyone is in the Ultrafast plans, as the plan is to upgrade most/everyone, but that could be 10, 15 or 20 years away! It also could be a badly worded email or they are using the wrong template. Perhaps it should say, "Thank you, we've registered your interest in our Ultrafast fibre rollout programme".
The full list of exhanges/areas up to 12 months in advance is openly published by BT,see this link https://www.openreach.com/fibre-broadband/fibre-firs...
then scroll down to the map and choose your closest city, you need to chose some location before it adds the shaded areas to the map. If you zoom out you can see just how little of the UK is under progress. There is also a link in the notes under the map that will take you to a document listing all the areas to be fibre enabled in the next 12 months.