hi lazyanttu,
The 'tip' strings are looked up in the faction lang file, this is a separate lang file that is located in techs/my_tech/factions/my_faction/ and should be named my_faction_en.lng, changing "my_faction" and 'en' as needed, of course
You can also include a tech wide lang file, techs/my_tech/my_tech_en.lng, in theory when a unit/command/level/etc name needs translating, it is looked up in the relevant faction lang file first, if not found there then it looks in the tech lang file, and if its not there then it would be looked up in the global lang file.
I say 'in theory' because there are likely numerous places where this doesn't happen atm, so if you notice anything you think may be wrong, please don't be shy, take a screen-shot and post it up, chances are it is an error and simply hasn't been noticed yet.
Cheers.