got my answers:
The generated search filter, *List.xhtml and *List.java, ignore all non-character columns, effectively not providing the option to search on Date or Numeric type columns.
Looking into the FreeMarkers template files generating *List.xhtml and *List.java - they seem to explicitly only process string(character) type columns - so this must be SEAM design decision.
Manually added non-character fields to *List.xhtml and *List.java are simply ignored.
This was my fault - new <param name...> definitions for the new fields must be also added to the *List.page.xml file.