On the SPNS site, if you look at the entry for "tigh" (following the links I mentioned above), you'll see among other notes "Angl. tea..." I'm taking this to mean that the Gaelic form is sometimes found Anglicised as "tea...", and I think it would be pronounced exactly the same. The "na" bit is found under "an" - as far as I can tell, this is something to do with Gaelic inflexions and how words change before or after vowels.
Arthur