It is owned by a non jew,and therefore can be open on shabbos.Just like other kosher non jewish businesses it is spot checked continuosly even on shabbos and yomim tovim.Mashgiach even found a violation and pulled hechsher from one of them.Additionally, all ingredients are reliable and most of the kosher franchises have their product made in a central location so easier to check on Kashrus.The ones on long Island are the same re ingredients and are checked by five towns Vaad.
BTW the hechsher under Rabbi Mehlman is not valid for baskin robbins in the store(as per sign posted which many people do not realize). He requires that only kosher flavors under KVH or Star D are in the stores he certifies donuts for, but refuses to give hechser on the fresh to order cakes and favors, they must have an individual hechsher from KVH or Star D as ice cream cakes can use different types of fillers and decorations including ones with non-kosher ingredients.