i have only short time to answer you.
in your situation :
activate C2 criterion on both cells
CRO of city cell = 6dB (or more)
Temporary offset = OdB
Penalty-time = 20s
CRO of highway cell = 0dB
Temporary Offset of HW cell = 6dB
Penalty-time of HW cell = 20s
HO Margin (city, HW) = 10dB (or more)
HO Margin (HW, city) = 5dB
ho margins do not modify behaviour with other neighbours.
if you have questions, let me know 🙂