Going slightly off topic here, but the reason they were ordered was the nature of the route demanded something that could do more than 39mph flat out (an E40Hs top speed at the time). The 17-plate batch were a follow on for a frequency upgrade. There may also have been issues with E400H leadtimes around that period, I can't quite remember - certainly delivery schedules were the reason Stagecoach London took 13001-32 which were Wright bodied B5LHs.
Really the route (73 Tayway) was never really suitable for hybrid operation, but as a flagship at the time it got the new, eco-friendly vehicles.
Back on topic, at a wild guess, the 62/112 E400Hs going to Metroline must mean Stagecoach are keeping 14 for Middleton (possibly swapping for the newer ones?) plus another 50....is that co-incidentally how many 13 plate E400Hs there are?