Is it possible to record 16 tracks at one time with audacity 
Only if you have a 16 channel sound card that is compatible with Audacity.
I have 2 m audio delta 1010lt cards installed. Audacity shows 12 tracks available. How do I get 12 tracks to show in devices ?
Audacity can only record from one device at a time, so unless you are somehow able to aggregate them into one device (I don’t think that is possible on Windows) then you will be limited to recording from one device at a time. Set the number of channels in Device Toolbar .
The situation with 1010LT is noted in the WIki http://wiki.audacityteam.org/wiki/Multichannel_Recording#Suggested_devices . If you are on Windows XP or can get the older 2007 drivers to work then you should be able to see a Multi device which will record eight channels.
If Audacity sees two Multi devices (one per card) then you might be able to aggregate them with VAC (not free) http://software.muzychenko.net/eng/vac.htm .
Also see this http://forums.m-audio.com/showthread.php?35772-Delta-1010LT-Multi-card-Setup-Solved .
Gale