Whomever seals the drawing, that's who takes the responsibility. I don't know the legal ins-and-outs as to how much, if any, liability the publisher of the "span charts" et al would be found to have in a court of law - and I suspect it depends on the case. But the EOR is the final say, and with him rests the final responsibility.Bottom line is the work is to be done either by or under the direct supervision of the engineer of record. It is up to the engineer of record to take responsibility for the design in whatever method they feel is adequate and then stand behind that design. However they justify their design is their business. This can lead to standard of care issues which varies from one area of the country to the other.
(Which is why the vast majority of us - Stan Caldwell excepted - think engineers aren't paid enough for this kind of thing).
N.B. Stan - I'M JUST KIDDING, OKAY!?!?!?!?