I think I understand now Marc – you are not syncing with Evernote, but instead just using local notebooks.
I can’t give you a definitive answer to your question, unfortunately. I would think that once the container was mounted, the contents could be synced across platforms with no problem using Dropbox. If you’re trying to sync the container itself, then I’m not sure if a Truecrypt container would sync across platforms or not.
Is there a reason that you don’t use Evernote to sync? Is it the lack of encryption on their end that worries you? That would solve some headaches for you, if you allowed everything to sync with Evernote after the drive was mounted on each machine.