I think the key parameter for GBRf/John Smith in expanding their traction options (e.g. buying these 47s and the 66s, reinstating the 92s etc.) is that it makes business/commercial sense for GBRf.
If you look a these three 47s, the only real use they'd had over the past year or so was on the Sleeper support work at Polmadie - firstly 739, then 749; with 727 stored all that time. After 749 and 739 swapped on the "beds support" role last Spring I believe 739 only made two round trips from/to Washwood Heath for loco moves. GBRf really have been the only FOC using, or planning to use, these 47s for the past year or so.
Not sure who made the first move, but somewhere along the line having the 3x 47s made sense to GBRf's traction options (i.e. for this new contract). 2 were serviceable and the third already undergoing overhaul for a return to traffic which helped too vs some other options. Colas had little use for them, and as above GBRf were the only people using them. Evidently a price was agreed that Colas were happy with in terms of selling in effect surplus locos which there were only going to get hire revenue from but would still need to maintain etc. and that GBRf were happy with as a more attractive option to continually hiring locos for a relatively long-term contract.
Whilst I wouldn't say I was expecting it to happen, the deal works well for both Colas and GBRf and made a lot of sense to me.
