The way I see it is that some of the lines which served reasonable sized settlements e.g. Louth, Cranleigh, Shepton Mallet, Wells, Queesbury, Henbury, Thornbury (Avon), Okehampton and Tavistock to name a few could be the ones that would be reopened first and even then the choice of rolling stock could well be class 139's, 230's, 399's, possibly more class 172's or if we're really desperate - class 143's / 144's or the seven class 155's.
Even then, the lines are very likley to be operated as single line working (to save money), using whatever is at hand (to save money) and its quite likley that if the line doesn't get off to a quick start then it'll be cut to a parly service (to save money).
Put it this way even if one railway line is reopened with Mr Grayling in office, then it'll be deemed as a success and quite rightly so.