Hi!
As Dieter has noticed, GSM traces from gammu / nokia DCT3 phones show the complete SYS INFO decode inside wireshark. However, the RSL messages BCCH INFORMATION do not decode it.
I've revolved this problem and submitted a patch to the wireshark team, you can get it from https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=4268
Please note: This patch does not yet address the problem for the SI5/SI6 in SACCH FILLING. The solution is not as easy, since in this case a generic L3 IE is handed of to the GSM_A_DTAP rather than GSM_A_CCCH dissector.
If anyone wants to help out with fixing this for the SACCH, I'm sure many OpenBSC users and wireshark guys will be happy to receive a patch/fix.
Regards, Harald