Users over at CrackBerry's forums have been reporting that they've been unable to switch their BBM account back to BlackBerry's legacy devices running BlackBerry's operating systems. Users have experienced a server issue that does not let you access contacts, groups, and channels after performing the switch back to a BlackBerry OS device. You can still hop around between BlackBerry OS devices, but if you move from a BlackBerry device to an Android-powered BlackBerry (or otherwise), iOS, or Windows device, you will not be able to successfully access BBM on a legacy BlackBerry...
Source: http://www.gsmarena.com/you_can_no_longer_switch_bbm_from_android_to_blackberry_legacy_devices-news-27063.php
