I haven't had such a client exactly but one would take a very graded approach to treatment. Much like the repair of a fractured scaphoid. Did they repair with simple fixation or did they need a graft from somewhere.
It might be useful to have a bone scan to see how active the healing process is right now. Think of the bone as something that has been unloaded whilst in the cast. It will take a good 12 weeks to continue to ossify and so the fracture right now is only being help together by the fixation. Add to that the fact that the fixation is best at day one and if anything loosens over time.
Mobilisation of the subtalar joint in AP/PA and lateral directions would assist and be no problem. I imagine they need some deep tissue massage to the soleus and gastroc. as well.
Look forward to hearing some more info on the client, history of the trauma etc 8o