I notice that Russian appears to have two different sets of rules defined - see the SVN file. One set is used in sentences with numbers, one in sentences without numbers. Can someone confirm that the software recognises which set of plural to use by whether the sentence contains the number or not? If this works for Russian, then presumably it could work for all languages, and would be of interest to some of the languages where the number 1 is in a group with other numbers. Please can a developer comment before I try to write this up on the plural page.
Languages lt, sh, sr and uk also appear to have 2 sets of rules, as for Russian.
Software doesn't recognize it. It just acts differently when less than usual number of forms are given (which is something that makes it hard to unify mediawiki rules with other systems).