To reuse them we had to write a compatibility layer. We needed to simulate some OSGi and Eclipse platform interface are replace them with dumb implementations. We managed to make it work, but we every upgrade of the Mylyn libraries we needed to provide and fake additional methods and interfaces. We knew this solution is very fragile.
For a while we wanted to replace the hacks with proper environment for Mylyn execution. NetBeans 7.1 finally includes Netbinox and can execute Mylyn in its natural environment without any hacks. Still, for proper usage outside of Eclipse we had to propose some enhancements.