Yes, it is possible. In fact, your Favorites are the only
thing you will be able to transfer. POI files and the like must be sent separately.
First, you'll need a copy of the old TomTom Transfer Assistant. I no longer find it on their web page, but am going to try to attach a copy of it for you here as a Zip format. It is an 8MB file, so even as an admin here, that may not be allowed. We'll see at the end... In any case, unzip the file and you'll get the executable that we need. [Edit: It's a bust. We'll need to get the *.exe file located on the TomTom site so that you can download it].
Connect your 5150 and run the Assistant. It will copy files to your PC, including your Favorites.
Then it will have you hit "Next" and then ask you to disconnect your 5150.
When Assistant asks you to "Connect TomTom device B to your computer", continue, but note that only
your Favorites (one from the previous list of things that you may have seen) can and will be transferred.
Click on "Transfer now" and your favorites should be moved to your new 520.
Where the heck has TomTom moved the Transfer Assistant on their web site???
The 8MB file is too big to attach here (unless I can get our board owner to open that up a bit), and is larger than Comcast is going to let me email, too! Help!