Two possible scenarios.
1) Nationalisation (i.e. outright confiscation). This was the Anglo route. In this case you will be entitled to compensation when some adjudicator eventually decides what was the worth of the confiscated shares. Anglo is yet to be decided. I presume the adjudicator will be assessing their perceived value at the time of confiscation, in which case recent share prices should be some indicator.
2) Purchasing additional shares and leaving the existing shares in float. This was the BoI/AIB route. In this case the value of the shares post the State intervention is in theory a mix of their value before and the price at which they are purchased. If these are the same then in theory no change. If the State buys at more than the closing market price then the shares should in theory go up in price and vice versa.
And this is what makes the process so very politically sensitive.
If this route is chosen then the State, from a PR perspective, is caught between purchasing new shares at 70c which was the price before the story broke, or at 38c which is the price at which they were suspended. 70c would seem more fair but the immediate result would be a bounce in the share price back towards 70c or even higher as sentiment would be good. Not very good headline
"shares soar 100% on State intervention". No wonder shares have been suspended.
I agree with Brendan that probably the second route may be chosen but it doesn't have the same logic as the BoI/AIB cases. In these latter the State hopes to rehabilitate the shares and sell them back, a market float helps.
In the case of ILP, the shares of the holding company will never be sold back. What would be logical to happen is for the State to sell the life company and then merge the bank with EBS. No obvious reason in my mind to keep a market float in the shares of the holding company. This could push us towards Option (1) above.