Hi Scott,
This is a good question that seems to pop up quite often. Of course, up to CCM 5.x licensing is really honor based so there is no report that you can query that will give you this info. Have a look at the following threads that go over this in some detail. Sankar really explains this very well!
http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Unified%20Communications%20and%20Video&topic=IP%20Telephony&CommCmd=MB%3Fcmd%3Dpass_through%26location%3Doutline%40%5E1%40%40.1ddc3dcb/0#selected_message
http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Unified%20Communications%20and%20Video&topic=IP%20Telephony&CommCmd=MB%3Fcmd%3Dpass_through%26location%3Doutline%40%5E1%40%40.1ddc57b7
If you wanted to estimate the applicable DLU's as they would apply in the CCM 5.X train you could query your set types and multiply by the appropriate model/DLU number.
Here is the DLU breakdown;
Cisco Unified IP Phone 7902G = 1
Cisco Unified IP Phone 7905G = 2
Cisco Unified IP Phone 7911G = 3
Cisco Unified IP Phone 7912G = 3
Cisco Unified Wireless IP Phone 7920 (no battery) = 4
Cisco Unified IP Conference Station 7936 = 3
Cisco Unified IP Phone 7940G = 4
Cisco Unified IP Phone 7941G = 4
Cisco Unified IP Phone 7941G-GE = 4
Cisco Unified IP Phone 7960G = 4
Cisco Unified IP Phone 7961G = 4
Cisco Unified IP Phone 7961G-GE = 4
Cisco Unified IP Phone 7970G = 5
Cisco Unified IP Phone 7971G = 5
Cisco Unified IP Phone 7985G = 6
Third-party SIP device (basic) = 3 (third-party)
Third-party SIP device (advanced) = 6 (third-party
From this doc;
http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_qanda_item0900aecd805009fc.shtml
Here is another excellent doc;
http://www.cisco.com/warp/public/765/tools/quickreference/ipphones.pdf
Hope this helps!
Rob
