Don't know about MacDill. Seems like if they were to get a new system, it'd be in the 380-390MHz range.
In my recent travels, getting hits on 14C in Seattle (the monster countrywide DoD system), there were some frequencies as high as the 406-408 range.
Also, the bands advertised by the 4A8 system's band plans include:
Iden 0 - base 851.00625, step 0.00625, FDMA.
Iden 1 - base 762.00625, step 0.00625, FDMA.
Iden 2 - base 851.01250, step 0.01250,
TDMA.
Iden 4 - base 380.00000, step 0.00625, FDMA.
Iden 5 - base 406.00000, step 0.00625, FDMA.
No, there is no Iden 3 broadcast, for some reason, at least not in my observations (and I monitored/analyzed for 11 minutes straight, so it's not like I missed it - unless it was missed coincidentally every time the CC data repeated).
Also note that it is TDMA capable in the 800 band. None of this means that it has any frequencies in the band - it could be for further system expansion, or could be the default band plans put on a system when it is being built.
In the control channel stream, there are opcodes with manfuacturer type 90, which indicates Motorola - so it's likely that this is a Motorola system (and thus,
if any TDMA is present, it will likely be X2-TDMA).