Hello,
The process will be done from Chandigarh RTO only
Though its slight inconvenient, but there are 2 reasons for it when we checked on it, long time back with one of the rto officer on it citing why Inter State HSRP Registration is not allowed :-
a) Will help in preventing theft cars to get HSRP number plate - generally theft cars been moved to other cities - so when-ever the HSRP process gets completed - a car without hsrp number plate found - it will be easy for cops to check on car documents and catch hold of it
b) As per Motor Vehicle Act, Section 47 - if a car is to be in a different state for more than 12 months then as per RTO Guidelines - that car should obtain a new registration mark of that state.
So - you may have to get high security plate from chandigarh only.