The ALX file is probably the closest equivalent to a JAD. ALX files define the elements of a BlackBerry application. They are required for installing apps using the BlackBerry Desktop Manager. You can generate one using the BlackBerry JDE (Project -> Generate ALX).
Also, here's a link that defines the elements of an ALX file: ALX Elements.
Here's a link to the BlackBerry Development Guide, which has a section on packing and distributing BB apps.
Finally, here's a link to a forum post about setting up a server for hosting BlackBerry apps for OTA download/install: OTA Server