@Oleh Lunin ,
While your changes don't work they did point out to me where the problem lies and I'm working on a solution.
I will post a revised CIV4ImprovementsInfos.xml for you to use to replace the one you are using in your game. Mountain Mine had no proper upgrade path to Core mine and none of the other Mines could upgrade to a Mountain Mine. Also Core Mines did not have permission to be built on Peaks either.
(On a side note I also have discovered why Dancing Hoskuld's Fine Clay was not showing up like he wanted too.)
Give me a minute or 2 and I will upload that revised ImprovementsInfos file. Your game is the perfect test for it to see if the changes work as designed.
EDIT: Try this in place of your current one. If it works correctly for you I will commit the changes to the SVN.
JosEPh