Yes, you only have to have the brake lights illuminated, not actually applying any brake pressure. Not all Z4's have the remote roof dropping feature (which is cool) but you can have it re-programmed by a technician. There are several people offering such services on eBay. One is located in Derby I think and he charges an amount to check all and any upgrades possible on your car. If you google it there is a post on there which tells you that 3 quick successive presses on your remote will do it. I haven't remembered to try it yet. One for tomorrow.
Tony.