The morning broke cool and gray, but power was still out in many businesses and hotels after Tuesday night’s smoky transformer fire, and people on the street in the Back Bay area wondered what the day held in store. At the Capital Grille restaurant on Boylston Street, workers navigated through the kitchen using flashlights. In the Prudential Center, employees wondered whether businesses would open for the day. At the scene of the fire on Scotia Street, passersby shot photos of the gaping holes left by the explosion. Jackie French, 55, of Annapolis, Md., was in town for a convention, staying at the Marriott. Last night, she, along with hundreds of other guests, suddenly found herself in the dark.