Yes, Bruce is buddypress 1.2.compatible,
you have two ways to achieve that:
1.
please download, install and activate the BuddyPress backwards compatibility plugin
2.
use the latest bruce built, copy your current css and rename it to css old
further steps for upgrading buddypress:
Upgrading from 1.1 to 1.2
1. Deactivate any BuddyPress plugins and then deactivate BuddyPress.
2. If you are not going to use the new default theme, please download, install and activate the BuddyPress backwards compatibility plugin.
3. Upgrade BuddyPress automatically, or download BuddyPress and overwrite your existing copy.
4. Delete “bp-default” and “bp-sn-parent” from your themes directory.
5. If you are using your own custom theme from 1.1, you will need to add define( 'BP_CLASSIC_TEMPLATE_STRUCTURE', true ); to your wp-config.php file above the “stop editing” line.
6. Activate BuddyPress. You do not need to move any themes in this version.