Meanwhile, back in Pacer related discussion...
GW are to deploy 110x 165/166 vehicles in the west between 2016-18 as the Thames valley gets wired. These are expected to displace 8x 143s and 19x 150/1 (and 150/0?) sets, with all other 15x classes retained and even the hybrid 150209 reformed and toilet fitted. That is a total of 27 Pacer displacements/withdrawls.
ScotRail are to release 8x 158s, 10x 156s and 29x 170s in 2017/18 when the full EGIP scheme & HST deployment is achieved. That is a total of 47 units for cascade schemes and eventual Pacer displacements/withdrawls.
LM should release their 6x 153s in 2017 when the Chase line goes live, doubts whether the 3x 150/1s can go too. That is a total of 3 (equivalent-ish) units for Pacer displacements/withdrawls.
Northern should been able to release something around 14 to 16 units (including the TPE load 156s) when Manchester-Bolton-Blackpool goes live in 2017, assuming that no units will be released this year because of Wigan/Chat Moss going live.
That all adds up to around 90 units displaced - almost equivalent to the 142 fleet. The potential 120 new build vehicles for Northern looks sufficient to bridge the gap to see off the other classes. I'd say that it looks possible that all three Pacer classes could well go by 2019/20, but the unknown is increasing demand which could well scupper this plan, whilst any delays in the electrification schemes will naturally have significant impacts, thus requiring short-term retention of the 144s.