Here for documentation the errors of the 6.20 drivers below precise.
A "no change backport" from raring was installed. Please keep in mind that an equivalent package already landed in precise-updates which will break the functionality also in this precise.

*-network
                description: Network controller
                product: BCM4312 802.11b/g LP-PHY
                vendor: Broadcom Corporation
                physical id: 0
                bus info: pci@0000:02:00.0
                version: 01
                width: 64 bits
                clock: 33MHz
                capabilities: pm msi pciexpress bus_master cap_list
                configuration: driver=b43-pci-bridge latency=0
                resources: irq:17 memory:56100000-56103fff

apt-cache policy bcmwl-kernel-source
bcmwl-kernel-source:
  Installed: 6.20.155.1+bdcom-0ubuntu6~precise1~ppa1
  Candidate: 6.20.155.1+bdcom-0ubuntu6~precise1~ppa1
  Version table:
 *** 6.20.155.1+bdcom-0ubuntu6~precise1~ppa1 0
        500 http://ppa.launchpad.net/dirk-computer42/c42-backport/ubuntu/ precise/main i386 

Apr 15 13:15:10 tai kernel: [  295.908018] Pid: 4294, comm: iwconfig Tainted: PF          O 3.8.0-18-generic #28~precise1-Ubuntu LENOVO 2957                            /Mariana2
Apr 15 13:15:10 tai kernel: [  295.908018] EIP: 0060:[<c15fd66e>] EFLAGS: 00010202 CPU: 1
Apr 15 13:15:10 tai kernel: [  295.908018] EIP is at wireless_process_ioctl.constprop.4+0x5e/0x1a0
Apr 15 13:15:10 tai kernel: [  295.908018] EAX: 00000000 EBX: f6182000 ECX: 00000000 EDX: 000000c8
Apr 15 13:15:10 tai kernel: [  295.908018] ESI: 00008b09 EDI: f368df14 EBP: f368dee0 ESP: f368dec8
Apr 15 13:15:10 tai kernel: [  295.908018]  DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
Apr 15 13:15:10 tai kernel: [  295.908018] CR0: 80050033 CR2: 000002f0 CR3: 2d123000 CR4: 000007f0
Apr 15 13:15:10 tai kernel: [  295.908018] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
Apr 15 13:15:10 tai kernel: [  295.908018] DR6: ffff0ff0 DR7: 00000400
Apr 15 13:15:10 tai kernel: [  295.908018] Process iwconfig (pid: 4294, ti=f368c000 task=f61be680 task.ti=f368c000)
Apr 15 13:15:10 tai kernel: [  295.908018] Stack:
Apr 15 13:15:10 tai kernel: [  295.908018]  f368ded8 c1629e58 00008b09 00008b09 ffffffe7 f368df14 f368df00 c15fd80b
Apr 15 13:15:10 tai kernel: [  295.908018]  f368def0 c1919280 00008b09 00008b09 ffffffe7 c1919280 f368df44 c154101e
Apr 15 13:15:10 tai kernel: [  295.908018]  bfb6c06c 00000000 bfb6c06c 6e616c77 00000030 00000000 00000000 f918cb73
Apr 15 13:15:10 tai kernel: [  295.908018] Call Trace:
Apr 15 13:15:10 tai kernel: [  295.908018]  [<c1629e58>] ? mutex_lock+0x18/0x40
Apr 15 13:15:10 tai kernel: [  295.908018]  [<c15fd80b>] wext_handle_ioctl+0x5b/0xd0
Apr 15 13:15:10 tai kernel: [  295.908018]  [<c154101e>] dev_ioctl+0xbe/0x290
Apr 15 13:15:10 tai kernel: [  295.908018]  [<f918cb73>] ? wl_ioctl+0x53/0x1b0 [wl]
Apr 15 13:15:10 tai kernel: [  295.908018]  [<c152a75b>] sock_ioctl+0x1ab/0x290
Apr 15 13:15:10 tai kernel: [  295.908018]  [<c152a5b0>] ? move_addr_to_user+0xb0/0xb0
Apr 15 13:15:10 tai kernel: [  295.908018]  [<c1173fdf>] do_vfs_ioctl+0x7f/0x2f0
Apr 15 13:15:10 tai kernel: [  295.908018]  [<c162cda0>] ? do_debug+0x180/0x180
Apr 15 13:15:10 tai kernel: [  295.908018]  [<c1019eb5>] ? fpu_finit+0x55/0x70
Apr 15 13:15:10 tai kernel: [  295.908018]  [<c11742c0>] sys_ioctl+0x70/0x80
Apr 15 13:15:10 tai kernel: [  295.908018]  [<c163340d>] sysenter_do_call+0x12/0x28
Apr 15 13:15:10 tai kernel: [  295.908018] Code: 0f 84 af 00 00 00 8b 53 2c b8 ed ff ff ff 83 e2 02 74 5e 8b 93 70 01 00 00 31 c9 8b 83 d8 00 00 00 85 d2 74 0c 8b 12 85 d2 74 06 <8b> 8a 28 02 00 00 85 c0 0f 84 e4 00 00 00 0f b7 48 04 8d 96 00
Apr 15 13:15:10 tai kernel: [  295.908018] EIP: [<c15fd66e>] wireless_process_ioctl.constprop.4+0x5e/0x1a0 SS:ESP 0068:f368dec8
Apr 15 13:15:10 tai kernel: [  295.908018] CR2: 00000000000002f0
Apr 15 13:15:10 tai kernel: [  296.154163] ---[ end trace daf76ea4b179d8bb ]---