An AT&T (T +1.2%) takeover of T-Mobile (OTCQX:DTEGY) would transform it into a "truly wireless-first carrier," which could be worth an additional $5/share, Sanford Bernstein's Craig Moffett writes. In contrast to skepticism about regulatory approval, Moffett thinks the deal “has a real chance of approval,” given the skills of AT&T’s regulatory team.