Well Peter Norvig switch from lisp to Python.., as also others googlers did when they saw that their teammates writing python where as productive or more than themselves using lisp.
And then choosing python for complex high performance work seems like asking for a headache at this point.
In terms of programming-in-the-large, at Google and elsewhere, I think that language choice is not as important as all the other choices: if you have the right overall architecture, the right team of programmers, the right development process that allows for rapid development with continuous improvement, then many languages will work for you; if you don't have those things you're in trouble regardless of your language choice.