LEC 2 is probably AT&T. (With congestion like that, I guess I won't bother to sign up for "GigaPower".) Verizon is LEC 1 or 3 and I'm not sure who the other LEC is.
Comcast? Comcast and Verizon were the big two Netflix signed deals with.
It's probably CenturyLink, which is the 3rd largest LEC behind AT&T and Verizon. (Comcast isn't classified as a Local Exchange Carrier, it a cable operator.)
It definitely is CenturyLink. Their Level 3 interconnects have been saturated for awhile, longer than March.
AT&T and Netflix signed an interconnection agreement, so LEC three must be CenturyLink (who also announced a 1Gb broadband trial in Portland)