Hi Alistair,
This is an excellent question :) With the release of CUCM 5.x the licensing model completly changed.
For all 3.x and 4.x versions (including CCM 4.2(x)) the CH-1 (Channel)Phone License was used and was really totally "honor" based. There was no License actually loaded "on-box" so this is why you can't find any references to them :) Now phones use DLU's (Device License Units) which are loaded on the CUCM First Node or Publisher server. The "Station License" has been replaced with the DLU (Device License Unit) in CCM 5.x and above, also the new model includes "Node and Software Feature" Licenses;
From this good Q & A doc;
http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_qanda_item0900aecd805009fc.shtml
Hope this helps!
Rob
