When we were in the PL, there were temporary facilities in the NE corner to server the fans who were housed there. These facilities, like the stand, were only given temporary permission and had to be removed. So there are no facilities in the north half of the east. If fans are in there, they either have to use the facilities in the North, so would have to be home fans, or the facilities under the south east, so they woul dhave to come along the side of the pitch past the press area and in front of the rest of the east. The facilities under the south-east can probably cope with 3k fans at a squeeze. There is also the issue of exit. Since the north was "reclaimed" there have been issues with fans mixing at the north east corner of the ground. This has been resolved by making exit gates into back henry street from the south half of the east, but it would still mean that any away fans in the north had to exit in the north east corner or trudge along close to the pitch towards the south. Neither option is ideal in a potentially tense/angry/hostile environment, and would require significant increase in stewarding and police. So the logistics of putting an extra 1000 fans in the north half of the east really don't add up. It may be that if they can definitely sell the whole north half, an extra 2.5k, in a match with low risk of misbehaviour, eg derby last season) then it makes financial sense to do it, but probably not a significant amount of profit to be made, and if that gives the away team any sort of boost, then it seems like not a good idea.