It will be interesting to see if that happens. All the ones that I have seen have a box outside and near ground level. I can't see any physical reason why it needs to be outside, but it does need to be near a stable surface as the equipment that they use to precisely align the ends of the cable and "weld" them together can't be used whilst balancing on a ladder. Let us know if they do install the "outside" box in your loft.
I made that aspect clear to YouFibre, at the beginning, that I both wanted it straight into the loft, and that they could not run any cables down the wall, because they always come adrift, flapping about - apart from looking unsightly. They agreed they could do that.