Yes, this is true, we have COMB potentials classes implemented in the ATK-Classical/TremoloX-calculator in ATK-2015.
We also have some predefined COMB-potentials such as:
COMB_OSi_2010 : Shan, T., Devine B., Hawkins, J., Asthagiri, A., Phillpot, S., Sinnot, S., "Second-generation charge-optimized many-body potential for Si/SiO2 and amorphous silica", Pysical Review B 82, 235302 (2010),
COMB_OSi_2007 : Yu, J., Sinnott, S., Phillpot, S., "Charge optimized many-body potential for the Si/SiO2 system", Pysical Review B 75, 085311 (2007)
You can directly use them from the ScriptGenerator.
I think the reference manual has not been updated to 2015 yet, that's why the classes are not in it. But, this will be changed very soon, and then you can also define your own COMB potential.
And yes, you can also use semi-empirical calculators for MD simulations. Just change the calculator in the ScriptGenerator and run the MD simulation as usual.