This may be by design but on my FreePBX 13 systems if I go into the Digium Phones Module > Firmware and search for firmware updates it will only give me versions up to 1.11 and those only for the D80’s
all other phone models the only firmware available is 1.4.2 from june of 2014.
Note on these systems the only phone models are D40/50/70’s
Not sure if that is the reason.
on other sytems with D60’s and above I get versions in the 2.x level