Is there a way to configure the Twitter app for Android to submit a push notification when a tweet by a user I'm following contains a specific hashing I'm interested in.
I don't know about the Twitter app, but if you're willing to use this site: https://ifttt.com/
then yes, it's possible.
At this point IFTTT does not appear to let you push tweets by a user other than yourself, so will not accomplish what is being asked.