Unfortunately I have zero experience with svg files so I cannot be much help here. My hunch is that it may have to do with how the XML is being processed and whether it is embedded or stand-alone – that is the complete extent of my knowledge of svg files. ;) I have also seen references to svg that look something like this: svg+text / image/svg+xml . What that means i have no idea. I guess google around to figure out what could be the problem so that you can come up with a solution – you have to know what the problem is before you can create a solution. ;)
http://googlewebmastercentral.blogspot.in/2010/08/google-now-indexes-svg.html