I have QGIS 2.10 (the CASE method works there) and 2.12 here at the moment. 2.12 shows the rule-based labelling but it does not work with the rule "ELEV" % 1000 = 0 even though it clearly finds all the elements when it is tested. Does it work properly in 2.14 and later then? I can try later on at home. Cheers