If information was found which could not have been obtained except by illegal means, that would indicate that illegal means were used in obtaining the information. Whether that is "spying" or not is a matter of definition. I suspect that a raid on most newspapers and political,parties could well come up with information that had been obtained illegally. Probably including the addresses of people who would rather not have their addresses known.

The important thing is whether the information has been gathered with the intention of using it to wage war or carry out assassinations. (Not "would be useful" in such an eventuality - anything can be useful, including many things which could be useful for other purposes.) That hasn't been demonstrated in this case, and I suggest it doesn't seem likely in the overall circumstances.

As for Bertie Aherne's much quoted statement about not sharing government with Sinn Fein, I'd view that with as much scepticism as that of any politician making a similar statement in the context of a political set-up dependent on building coalitions where Sinn Fein's support was not needed. If he needs Sinn Fein support at some future time, I predict he'll make a deal. Or some one else will.