MBTA officials are investigating whether a public vote to choose the exterior designs for the agency's Green, Orange, and Red Line cars was invalid, a spokesman said."MBTA tech staff is looking into evidence of some irregular voting patterns," T spokesman Joe Pesaturo told the Herald when asked about statistics that indicate the voting process wasn't on the level.Pesaturo said officials were also "reaching out to Survey Monkey, the makers of the program that was used to solicit responses."