I'm not so sure about that... BHP has a long stated preference for volume over price. And POT's mine utilization is quite low. If they bought POT, they could easily ramp up and keep prices at $300/ton forever.
However, on the balance, if BHP is committed to Jansen (in lieu of acquiring POT), it would be better for us if they bought POT and left Jansen for future development when supply/demand is more in balance.