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.
EDIT: Disregard this I'm dumb
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)