Whilst I'm all for open source in government, I can;t help thinking every time they come out with press releases saying "we used " describes a process where being different with the technology stack is an end in itself.
You could write an open source application in C++ rather than the much less mainstream R language and you'd have lots of people ready skilled to maintain it. Using R just seems like it was the choice of the devs who persuaded the agency to adopt their tools rather than an agency who thought about what they needed up front.
I wonder in 5 years if we see headlines "Immigration Agency dumps open source for Oracle. A spokeperson said,'we used a bunch of obscure languages and tools for the old system that served us well we had difficult finding people skilled in them, so we successfully outsourced the system to our new partners who will deliver increased performance and efficiency savings over.blah blah blah". If they'd done it "maturely" in the first place, this kind of nightmare scenario wouldn't happen.
(and I speak of experience - currently discussing details with a company that has a system "built with a mix of Erlang, Scala and Ruby on Rails". You know its been cobbled together by a bunch of hacks more interested in whatever language seemed coolest at the time.