It is good to understand how these systems works.

The peice of information that seems to be missing It what kind of signal was recieved after the initial 911 button on the Spot.
Admittedly I didn't read the original report.

1. Did the Spot continue to send 911 signals after the initial signal?
if it did contnue to signal for more the 30 minutes it seems odd that it never sent a GPS Signal, Would seem to inidcate that it was in a postion that would not allow it to recieve a GPS signal. If it did signal for more than 30 minutes then the 406 PLB would have been a huge advantage due to the Doppler trianglation feature.
if it did not transmit for more than 30 minutes, Then it would seem likely that whatever stopped the SPOT signal would likely have stopped the PLB GPSsignal also(if it was a GPS equiped PLB), making doppler tracking at least limited if not useless, In which case it appears the SAR response would have been the same as the SPOT response, ie. attempt to notifiy the contacts associated with the device.

True the PLB signal is techically more reliable than the SPOT so it is possible it might have continued to signal when the SPOT could not, but I don't thnk we have any way to know this.

Of couse if the SPOT had been using the Tracking feature with the unit positioned in a good reception position it would have been a non issue, even if it had missed a few position reports it would have reported enough to initate a search once the 911 one initated.

Brian