Looks fine, but the Build-Depends should probably be libjson-c-dev instead.
Note; I'm looking at the upstart binary package and it looks like it probably doesn't need to Depends on libjson at all, and the upstart-bin package appears to already Depends on libjson-c2 via shlibs:Depends, so you might as well remove it from there too :)
With these changes made I think things will be just fine to merge and upload.
Looks fine, but the Build-Depends should probably be libjson-c-dev instead.
Note; I'm looking at the upstart binary package and it looks like it probably doesn't need to Depends on libjson at all, and the upstart-bin package appears to already Depends on libjson-c2 via shlibs:Depends, so you might as well remove it from there too :)
With these changes made I think things will be just fine to merge and upload.