Some issues to note:
Productivity of the language (including tools - IDE, debugger, etc)
Employable set of people who have that particular language skills
"popularity" of the language
People in your organization who have the language skills
difficulty in learning the language
portability of the language/platform support
applicability to the problem domain (I.E. device driver and python most likely is not a good idea)
There are others.
In some places I have seen horrible mandates on language choice by managers who did not understand new-fangled languages like C++ so they would only allow C. Or there are managers who believe all the hype and press and choose, for example, Ruby where it has no business being.
Most often it comes down to one that your organiation has competency with and is mostly suitable for the doamin.
If you want to incorporate a new language for your organization roll it out with test/small/trial projects.
