How to query mysql tables with regular expressions?
I answer by myself. In short, sql syntax above is correct, so how to query mysql tables with regular expressions? Exactly like I did.

The reason why it didn't work, is regexp syntax being too 'complex' for mysql.
I found out that mysql doesn't support the full syntax possibilities of standard regular expressions. I must use simpler symbols/constructs. So for example, instead of \D{2} I can use [A-Z]{2}, and instead of \d, knowing I'll want 1 or 2, I can use [1,2]?. A syntax like the following will perfectly work in mysql to match a string like 'IT.1.12.00.00.00':

[A-Z]{2}\.[1,2]?\.[1-9][0-9](\.00){3}


With full regexp syntax I could have use lookahead assertions and other constructs, but anyway, for now for my needs I can use plain 'old' grammar.