Do Bethesda have any noteworthy policies on their lore and when expanding the TES universe?
Presumably. Sometimes it's hard to tell.
I've heard some whispers about everything that have happened on Nirn have a real life counterpart... Or something along those lines...
No. To put it simply - no. Not if they're doing it right, anyway.
And how much does the lore influence the games? Does it matter much to everyone that works on the games, even the data programmers?
Only so much. It probably outlines/is molded by the 'Main Quest', but otherwise your average dev probably isn't up on his lore. Take, for instance, the questers of Oblivion. Or, if they were up on their lore, they don't really concern themselves with 'canon' etc. There's probably some guy whose job it is to give things a quick once over (at the quest design stage, likely) to check for glaring lore errors, but otherwise, they probably don't worry about it.