If a company is embarking on a share repurchase (buyback), I...

If a company is embarking on a share repurchase (buyback), I think it has to notify the market in advance. I'll need to check this so if someone knows for sure, please say. I doubt CNP is doing this - if they had the capital, they'd use it to pay down debt.

In answer to your second question, a disclosure relates to shares owned by all related entities.

As I have said before, one party could have an agreement to buy shares from another party at a point in the future and I guess this could be a way to circumvent the immediate disclosure if they were planning a takeover.