Here is additional information to help others...
ActiveWirelessClients (for 2.4Ghz radio) = OID: 1.3.6.1.4.1.9.9.273.1.1.2.1.1.1
ActiveWirelessClients (for 5Ghz radio) = OID: 1.3.6.1.4.1.9.9.273.1.1.2.1.1.2
...this will return a number, the number is how many clients are associated
Dot11Radio0 (2.4Ghz) status = OID: 1.3.6.1.2.1.2.2.1.8.1
Dot11Radio1 (5Ghz) status = OID: 1.3.6.1.2.1.2.2.1.8.2
...this will return the number "1" if it is working normally, otherwise as follows...
"The current operational state of the interface.
The testing(3) state indicates that no operational packets can be passed.
If ifAdminStatus is down(2) then ifOperStatus should be down(2).
If ifAdminStatus is changed to up(1) then ifOperStatus should change to up(1)
If the interface is ready to transmit and receive network traffic; it should change
to dormant(5) if the interface is waiting for external actions (such as a serial
line waiting for an incoming connection); it should remain in the down(2) state
if and only if there is a fault that prevents it from going to the up(1) state;
it should remain in the notPresent(6) state if the interface has missing
(typically, hardware) components."
Unfortunatly, on both v3 and v6 hardware revisions (according to back sticker) of Autonomous 1142N access points I'm finding that the 2.4Ghz or sometimes 5Ghz radio will randomly go down, for no discernable reason at all :-( The only thing that brings it back up is to manually go into the GUI and set it to disabled, then enable it again - or reboot the AP by removing power for 10 seconds.