Not answering your question fully but hopefully this might help -
The IE Domain Registry is the body you should contact, and they have a Dispute policy.
From
IE Domain Registry - domains may be registered in any of the following categories:
Personal Name
Corporate Name
Registered Trade Mark Name
Registered Business Name
State Agency Name
Publication Name
Educational Institution Name
Politician's Name
Unincorporated Association Name
Personal Trading Name
Discretionary Name
The Irish Domain Registry only awards a .ie name after adequate evidence has been provided by the applicant that they are entitled to a particular domain name.
There can be other reasons for being able to obtain "WHATEVER".ie than simply having a company entitled "WHATEVER", so I think you may not be in a position to force the domain owner to hand it over to you. You could see if they were willing to sell it to you.
It's a pity the CRO website doesn't warn people about this problem, I'm sure you're not the first to get caught out this way. I set up a company recently but I knew that there were various ways of getting a .ie domain so I spent ages checking availability of names, my first dozen or so ideas were gone! Eventually I found a name that was free, registered the .com and .co.uk, had the company set up and then was able to get the .ie domain.
I'd be curious to hear how you get on if you do try have do have something done about it.