Setting global source tree to find MYUtilities is invasive
Being forced to create a source tree to include MYUtilities into the project is unusual, annoying, invasive and not sustainable.
Source Trees are NOT good solutions to external dependencies (outside of single organisations). Requiring people to use source-trees merely to include this chunk of code isn't a good idea. It would be better if you merely included the MYUtilities source inside the Murky project.
Hopefully future versions of mercurial will make these kinds of problems go away.