  We discuss the current and prospective limits that can be placed on
supersymmetric contributions to $b\to s$ transitions in the Minimal
Supersymmetric Standard Model with general flavour mixing amongst the squarks.
We consider three processes: $\bar{B}\to X_s\gamma$, $\bar{B}_s\mu^+\mu^-$ and
$\bar{B}_s-B_s$ mixing, and pay particular attention to the large $\tan\beta$
regime and beyond leading order contributions where the difference between our
analysis and previous analyses is most pronounced. We find that even present
limits on BR$(\bar{B}_s\mu^+\mu^-)$ and $\Delta m_{B_s}$ often provide
additional constraints on the amount of flavour violation still allowed by
BR$(\bar{B}\to X_s\gamma)$. Limits on supersymmetric and Higgs mass parameters
can also be strongly dependent on the flavour violation. In particular, the
case $\mu<0$ can still be allowed, even for light sparticle masses. We discuss
how future measurements at the Tevatron, the LHC and elsewhere can improve
present limits but also provide unique signatures for the existence of flavour
violation.
