No.Because, depending on model year, the mount port is intended for the dedicated TomTom Blue&Me or TomTom Blue&Me2 satnavs only.
The port essentially only supplies power to the mounting cradle. The cradle comes with the dedicated B&M /B&M2 TomTom satnav(or can be bought separately on ebay).
So the cradle in turn carries a series of contacts to power the appropriate TomTom unit when it is clipped into place- the 1000Go and 5150 also use, I believe, the same contacts,hence they too could also be mounted in the holder cradle.But why bother, a cradle is about £50, just to save a power cable being visible.
I suppose that,in theory, if you could modify a Garmin unit to work off the B&M power contacts ,and cut away the casing to install the contacts (which you'd need to extract from a TomTom anyway), it would be possible- but as I said,you would only bypass using the in-car power cable for a Garmin, and would gain no other functionality, as the rest of the B&M/B&M2 functionality is bluetooth...............