What if it is fact? That doesn't mean it will happen!!
Reports are written all the time, to look at costs, timescales, options, capabilities, etc, etc.
No doubt during the SDSR a variety of reports were written, on a number of options, it didn't mean those options were taken up.
This could be a BAE internal report, to enable them to having costings/options up their sleeve if so asked - and to actually get the costs right this time.
It could be an MOD sponsored/funded report, so the next time someone in government asks "...how much would it cost for the UK to get back into the MPA game..", the answer, "..the last time this was examined was in 2011, when the cheapest cost/least capable option was assessed to cost £X billion, with an estimated in service date of YY months from initiation. Of course minister, costing may well have risen since then...", all said in a Sir Humphrey type voice, will be readily available!
Fact or fiction, the possible existence of such a report in itself doesn't mean anything at his stage of the game!