Interview with NetworkManager developer Dan Williams

"a) wireless network with same SSID's are not necessarily the same network 
(grrrr, linksys)."

True, but if it distinguished networks by the AP's BSSID (MAC address) then it wouldn't work
properly with multi-cell networks, which are exactly what ESSID enables. Interestingly, if you
disable ESSID broadcasts then it can recognise the network by BSSID. So it might not be too
hard to add the option to recognise other networks that way too.