So, this is kind of breaking redesign news. Many of you here have likely seen the backstage photos of the HE train cabins with the big bump sticking out of one side to accommodate some kind of 3D wizardry. I estimate the depth of those odd bumps to be 4-5 feet beyond the train cabins normal dimensions.
Weeeeeell... looking back at some nefarious digital photos of "things", none of the loading platform buildings, most importantly Kings Cross, was originally designed for that huge bump we see now. The trains were all quite standard widths in said "things" and were set to be maybe 6-12 inches from the opposite wall in the station.
So, each of the stations had to have been reeeee-engineered to handle the additional width of the final solution to the trains biggest effect. I would imagine that the redesigns or modifications happened 4-8 months ago but it might have been longer.
Perhaps they made an eleventh hour change to the design because they realized there needed to be greater distance between the passengers and the projection/screens for the effect to be completely believable (or if they are using some sort of layered screen technology, maybe they decided to create greater spacing between the screen layers). Whatever the reason, redesigning the stations at the last minute sounds Herculean.