yes, that seems to be logical : the si2quater should be only broadcasted on the BCCH, not sent on the SACCH.
If your TEMS is receiving it, it means
1) the network sent it on the SACCH (but perhaps that is an acceptable behaviour definde in 3GPP ? you didn’t find anything about this ?) (please check that this message was indeed received on the SACCH channel, if possible)
2) the TEMS ms has listened to the BCCH during the call setup (weird)
3) the TEMS software is going crazy and displays this message too late (weird too)
Do you have anything else in mind ?
I would go for answer 1) and contact RanOpt to report the issue.