isdayEnabled and dayStyleClass are not related to model but used just for client side disablement/styling. http://livedemo.exadel.com/richfaces-demo/richfaces/calendar.jsf?tab=clientSideCustomization&cid=44621
dataModel perform the same but returns statuses for each day using that methods. additionally it returns data which could be used in markup..
I'm not sure about info you need additionally.