On what server I'll need to have Apache 2.2, on one where .htaccess is located (opensearch.domain.com) or on destination one (domain.com)?
On the opensearch.example.com server. Then you can try the B flag
http://httpd.apache.org/docs/2.2/mod/mod_rewrite.html#rewriterule wrote:'B' (escape backreferences)
Apache has to unescape URLs before mapping them, so backreferences will be unescaped at the time they are applied. Using the B flag, non-alphanumeric characters in backreferences will be escaped. For example, consider the rule:
RewriteRule ^(.*)$ index.php?show=$1
This will map /C++ to index.php?show=/C++. But it will also map /C%2b%2b to index.php?show=/C++, because the %2b has been unescaped. With the B flag, it will instead map to index.php?show=/C%2b%2b.
This escaping is particularly necessary in a proxy situation, when the backend may break if presented with an unescaped URL.