The BMW ActiveE field trial will be similar to the MINI-E lease program that I am currently in and will start sometime in late spring/early summer of 2011. Complete details have not yet been announced but will be shortly. You can get the latest ActiveE information here and all official ActiveE information as well as how to apply to be in the program on the official BMW ActiveE website that can be found at THIS LINK.
Check frequently because the application process will not be open for a long time. I believe the information on how to apply will be posted in the near future so keep checking if you are really interested. I say go for it, you won't regret it!