There is a feature request opened for such case, https://jira.atlassian.com/browse/CRUC-1058, but it doesn't seem to be a highly demanded feature so I won't expect that to be implemented soon I am afraid.
I haven't tried that personally but I can see there are some tools on the market to migrate MKS into other SCMS (git, svn, perhaps others) which are supported by FishEye/Crucible. Perhaps you want to give a try? For example you could try seting up a on-the-fly migration from MKS to git/svn and index that git/svn mirror of your repository? Take a look at:
Hope that helps,
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