Yandar, that is not entirely true. You can do OTA activations on BESx if you have a BES data plan. If you have a BIS data plan, you're stuck with a wired activation. I have done 6 BESx installations, with ~5 wireless and ~15 wired activations. If you have access to the BlackBerry Expert Support Center, there is an Enterprise Activation Readiness Tool that can tell you if a handheld can do OTA or not, provided you have the PIN and IMEI/MEID.
The document i linked to above has instructions for BES 5.0 to do OTA OS upgrades (starting at page 20), and all the options exist in BESx. I just haven't actually tried it yet, but I believe it should work (why else would the options be in the console?)