Is it possible for the BL600 to download a smartBASIC program over the air?

Yes, BL600 smartBASIC programs can be loaded over the air by booting into VSP mode. Please refer to the Virtual Serial Port Service section of the smartBASIC  BL600 extensions document which can be found at this link.

Note the behaviour if a $autorun$ program exists, which may require you to include the ERASEFILESYTEM function in your smartBASIC program to erase any existing $autorun$ program prior to loading a new smartBASIC program.