I define a rewrite rule on an init hook like:
add_rewrite_rule( 'foobar/(abc|def|ghi)/(.+)(/(\d.+))', 'index.php?my_action=$matches[1]&my_name=$matches[2]&my_version=$matches[4]', 'top');
This works with following URL on a single WP installation:
http://example.com/foobar/def/whatever/1.2
However it doesn't on the multisite installation.
It seems there's problem with rewrite rules on multisite an there's ticket #19896 which describes a similar problem on "non WP rules"
I have no idea what I should add to the .htaccess file and I prefer a "proper" solution.