Is austria JAA or ICAO
Both. All members of the JAA are also members of ICAO
I will be in austria later this year and would like to validate my atp,is this possible ?
No. You cannot 'validate' your ATP in any JAA state. Perhaps you mean to ask if you can get a JAA ATP issued in Austria on the strength of your non-JAA licence, in which case the answer is still no. The JAA website is perfectly clear on the status of Austria.
This tells you that Austria is a member of the JAA and
this tells you that they are not yet recommended for mutual recognition and so cannot issue JAA licences.