Some Non-Cash ‘Carrots’
In one case I worked with development team that wasn't keen to try pair programming. However, I observed that they were using pretty old computers for development and they were not happy with the performance.
Therefore I purchased a couple of high-end workstation, shiny, brand-new and fast, along with really nice large flat panel displays. I also got a desk for each of them so it would be easy for two people to sit next to each other on those desks. And finally I announced the rule that these boxes are dedicated to pair programming hence the powerful machines.
It didn't take long for the 'carrots' to show an effect. Slowly first but then more and more people tried it. Some only for a short time, some for more. And eventually I had to get more such machines and the team was totally hooked.
In a different case I was working with a team that was sitting on very old C++ code. The available tool set was appalling, and so I gave the team the direction to get onto Microsoft .NET, in particular C# where a much better tool set would be available, including good refactoring support, unit testing, and better libraries. And all the memory management crap would disappear as well.
Again it was close to impossible to get there. And some of the reasons given were just fine. For instance there were significant technical obstacles to make that shift easy.
Therefore I asked one of the team members to find out how to move the native C++ code to Managed C++. Sure, that wasn't straight forward either but it was an enabler and good step in the right direction. As a consequence it became much easier for the team to mix and match Managed C++ and C#. And since the tool support in C# was much better, more and more code was eventually written in C#.
These are just two cases where using an appropriate 'carrot' helped the team to move faster towards a desired outcome. Sure, in particular the second example is a bit special. Yet, I am sure that you are able to find more 'carrots' which work in your particular situation. I'd be interested in what you find out!