New Englanders will likely pronounce it medda dayda. Since there is no R in either word, Bostoners won't be leaving it out.
I could be wrong about the long A in data. I'm not actually from New England*, so my accent has variants, and it's possible that's one I don't know about. But that's how I pronounce it.
*Both parents grew up in Pittsfield. I inherited the accent and the attitude. I even drive like them.