No need - all you need is an insider
These guys deal in fear. Disclosure costs a company gazillions in lost customer confidence and bad publicity. If I were to run a job like that I'd buy myself some good quality inside files from a techie in ops, which is a cheap investment. Mostly beer and some threats to relatives - job done.
At that point you have data to make it credible you have somehow managed to hack into the core, and after that it's balancing publicity, security and so haggling.
Cheap, high return on investment, and no real need to be 'l33t' hackorz.
Most companies don't manage systems tight enough to disprove your claim, so they would either have to won up to that or pay.
And here endeth today's lesson about thinking like a criminal.