If you are prone to MPB, don't use Trenbolone, it will make matter worse, no matter if you use it with Finasteride, or without it.
If you are interested in detailes, yes, Finasteride will prevent reduction of Trenbolone to less androgenic metabolite, but, it will be still androgenic enough to speed up your hairloss.
If you are not experiencing hairloss now, give it a try, but don't use Proscar/Propecia.