it does not demonstrate anything , as even if the IEP order had been fulfilled with locos and hauled stock there would still be issues with the ballance of traction if the electrification work and commissioning doesn;t match the presumed case for the stock at the point of delivery - the difference instead of bolting some extra powerpacks in is is an order for locos to cover the period in question or rental /lease of of existing locos (55? 57 ? 67? 68 ? ) or HST sets to cover the period of uncertainty ...
Indeed, so rather that is costing the government/NR/the TOC the cost of 4 extra engines and associated tanks per set which needs to be converted to bi-modal operation it would cost them 1 (or more likely from what others have said 2) locos per set which is being hauled away from the wires. Given that RAGNARØKR has in the past claimed that a loco costs £2.5 million, for every loco that would mean that you could convert 3 sets if it cost £200,000 per engine and tank set (which is likely to be significantly higher than it will be).
Given that (IIRC) the engines are leased and Hitachi's desire to expand into Europe (including possible future UK trains) and the number of engines the 800's/801's/AT300's will have going forward (even before this by my calculations over 350), I doubt there would be a problem (read small cost) with the need for up to 84 engines (assuming ALL the GW 801's go bimodal, in reality I would guess at less than all of them would need doing, even if there was no wires west of Bristol) being used for a short time and then becoming useful as replacements for units which go wrong (bearing in mind engines could be swapped in and out) and/or for new sets and/or training.
There is always the possibility that less than 4 extra engines per set are needed to provide a reasonably timed service between the end of the wires and the end of the route. It could well be that due to line speeds a reduction in the rate of acceleration and associated top speed could be lowered by using a total of 4 engines (or even 3 engines, although acceleration would likely be hit hard) per set rather than a total of 5.