"If providing source codes to DARA were a pre-condition to winning the order, in most cases source codes would be provided."
Absolutely no way in the world that would ever happen, Jacko! Such code is so commercially sensitive that divisions within a multi-national conglomerate won't even pass information to eachother, let alone to the customer.
On this occasion (scarily), pr00ne is correct. Even though 't Bungling Baron and his cronies have been causing budget and project overrun since time immemorial, the only way ahead is for close liaison with the OEM.
Can't wait to see how the Spannering Branch think that they will cope with an Airbus product - unless they wise up to through-life product support, that is!