The problem stems from your use of NONE as the database default, column and connection character set. It essentially means 'no character set, use whatever bytes sent as is'. For the basic ASCII set this will usually work fine. For other characters it can lead to all kinds of weird problems.
For your view definition you can probably get it to work by explicitly casting the column to a character set with Cyrillic characters (win1251), and by using the character set introducer for the literal:
Cast(theColumn as varchar(100) character set win1251) = _win1251 '<cyrillic chars>'
Better yet would be to use an explicit character set for your database default, columns and connection. With explicit character sets, firebird will convert for you between character sets, if possible.