@Nikolay - U probably meant 'National Frequencies' instead of National TV?
There can be national frequencies (Public) and national frequencies (Private) - there r usually many private TV's with national frequencies, but it doesn't make them national (public) TV.
EBU members r Public TVs, funded by public money (ppl pay for Public TV admission), or in some countries state budget.
I think only sometimes Private TV can become EBU member but has to have 'public mission' whatever EBU thinks is public mission. (I guess they wouldn't accept commercial chalga TVs in EBU), that's why BNT should be open for chalga, I don't see how otherwise chalga singers can go to the ESC.