Thanks for the bump. It turns out that due to the design of the button, it cannot function in the manner you're suggesting.
One of the many issues is as follows:
The button BLF monitors ext801 but speed dials 802.
when 801 rings and you press the button using call pickup, normally it should pick up 801, but if configured as a speed dial for 802, it would dial 802 and leave 801 ringing... and so on.
So unfortunately, the answer is no, the BLF button can only call pickup and speed dial the same extension as what is being monitored with BLF.
Great question though.