theory of a new substantial holder

Would like to discuss the potential of a new substantial holder...

First of all lets put a few things down: total ordinary shares approx 850million. A new substantial holder has to give 2 business days notice once gaining 5% or more. This would be equivalent to about 42million shares. In the last 2 trading days, 250million shares have traded hands.

Last time this many shares traded in a short time was mid Jan and mid Dec. With quite a few changes of holdings disclosed on ASX. I would definitely be expecting to see at least a notice or 2 on monday, latest tuesday.

Possible scenario:
1. Any new substantial holding couldn't be any of the interested parties who have had access to the data rooms. This would be insider trading.
2. Someone has confidence in the company and has bought up big knowing the company is grossly undervalued - investor or institutions..
3. Someone preparing for a hostile takeover - If this was the case, could it work as: basically once 5% is reached you have a further 2 days to accumulate as many shares as possible before disclosing to ASX, in order to take advantage of a low share price, before proceeding with a hostile takeover offer.

I think corporations law says you can only acquire up to 20% before having to make a takeover offer, but could be wrong on this?

So 3. You would acquire about 170million shares, (250m traded last 2 days), then possibly monday or tuesday, make a takeover offer on the company - even say $1.20-$2 to buy the remaining company. Potentially someone could buy 20% CNP at about 40c*170million shares = $68m, + the remaining 80% at somewhere between $820m to $1.4b. Total paid about $900m-$1.5b. Bargain? Possibly...