GSM specs doubt

[Gerard]

Hi list,
while studing burst_ind (I know that burst_ind must be used in a own controlled
network) i see that one SDCCH for a specific operator has been shared by more
than one MS (different TMSIs), some MS use for SMS other use for calls. Is that
an interpratation error (due the fact of using burst_ind in real networks) or
that could be possible? i didn't find explanations on sepcs.

TIA