I am not an opiate addict nor am I a doctor but I do believe his choosing suboxone over heroin is a very positive thing.
His lying about it to you is terrible, but shame is a very real thing we alcoholics and addicts struggle with every day.
I think the major caveat here is the OP's point that it would be easier for him to get heroin than soboxone, and he's opting for the latter.
And I have read a lot about how doctors specializing in soboxone treatment can run some pretty suspect practices.
To the OP, is your boyfrien steeped in a program of recovery like NA?