I stopped at my smart dealership today and asked if there was any way to find out a delivery schedule. They indicated I would have to call smartUSA, so I did.
What I was told (which others have already mentioned here) was that there
currently is no way to tell when any particular car will arrive based on the confirmation number (mine ends in 1203 by the way). They did indicate that a tool is being developed that will allow checking the status, and that tool is expected to be complete in late March. She suggested I call back on April 1st ;) to which I replied "and I'm supposed to believe what you tell me then?"

So, she then suggested I call back on the 2nd.
Anyway, as an additional estimation (that's the best that can be done at the moment), she indicated that the deliveries are being done 3~4 months after the final configuration confirmation. This estimate is based on January deliveries of vehicles configured in September, and February deliveries of vehicles configured in October.
So, while the last four numbers may indicate a relative date on where you stand in some line, the real telltale seems to be the time frame you configured your vehicle. In my case the configuration was confirmed December 7th, so I will keep my fingers crossed for March or April delivery.
