It is not possible. Objectify is a very simple and convenient lightweight ORM that sits on top of a GAE Datastore, thus shielding the developer from most of the complexities of using JDO/JPA.
Nowhere in the documentation have I seen the scenario you describe mentioned because that is not the problem it is trying to solve.
I suspect what you will probably need to do is create a Web Service that exposes your GAE application (whose data you want) through an API. Then have your other GAE application call those service methods to obtain the data it needs.
Alternatively, you can use something called remote_api. It allows you to access and manipulate a GAE Datastore remotely.
Below are some links I just found to similar questions after posting my answer:
Can I access Datastore entities of my other Google App Engine Applications
Can one application access other applications data querying the key in Google App Engine?