i tested the issue using 4.5
when i enter a number i get a string as a context object (correct)
when i navigate on the call log i get a PhoneCallLog object (correct - was not working prior)
when i look up a name i get null as a context object (still not working)
the only thing the native phone application does better is looking up names, the API for this is unusably slow if there are more contacts in the addressbook. too bad you still can not use the native app via a menu entry :(