Google Earth will display Mspsource derived routes and tracks quite happily.
The earliest versions of MS didn't handle the KML/Z files properly.
MS suffered the same user-resistance, hiccups, glitches and cross-platform problems which folk are expressing nowadays with BaseCamp; you were all willing Beta-testers for Garmin. So, no change there
.Also, IIRC, user tools were very limited on the early release versions of GE, too – so I doubt very much the "import" facility was in GE in those days.
I gave up on MS as soon as BC arrived.
