Ok I would first like to state that I am not a developer just a good old fashion geek, however im certain that with a bit of investigation and effort the maps currently used by Garmin connect can be replaced on a per user basis.
I believe at this that the application itself has not changed, its only the physical maps which are called.
Reviewing the code and the way the website behaves using the following tools available for the firefox web browser:
1) firebug
2) pagespeed
3) addblock plus
Along with reviewing the source code l currently believe that the intergration seems to be based around a flash api called umap : http://www.afcomponents.com/components/umap_as3/docs/
At this moment I believe the bing map info may be called from the following MicrosoftSettings.xml file:
http://umap.s3.amazonaws.com/assets/xml/MicrosoftSettings.xml
I believe that google maps info may have been called from the following GoogleSettings.xml file:
http://umap.s3.amazonaws.com/assets/xml/GoogleSettings.xml
As such I believe that using a browser plugin which permits the modification of webpages such as greasemonkey for firefox will permit code to be written to replace the bing maps with googlemaps.
My javascript skill set is lacking as such im trying to read up on how to do this with greasemonkey. Should anyone else whish to have a go please do.
Like I said im no developer and have no idea for certain if this is how the maps are called but the site most certainly currently refrences the MicrosoftSettings.xml file at this time. I also other websites using google maps refrenced the GoogleSettings.xml file as such this seems a good place to start as any.
If you can not help with coding, but are technically minded please review as much as you can and provide any URL's you think the maps are pulled from and any ideas or suggestions you have.
NOTE : Garmin state running firebug slows down performance of garmin connect, read the following URL for more details:- https://forums.garmin.com/showthread.php?p=43015