Where is a good place to look for standard equations on transmisison line regulation, line losses, and also, information on use of transposition structures to manage the above?
Lots of things to look at in faq238-1287. Transposition is much more of an ideal than a reality as most lines are not transposed and the lines that could benefit most from transposition are those least likely to be transposed, lines in parallel with other lines.
If you have two lines in parallel, one line need three positions or two intermediate transpositions but the other line then needs to be in all three positions for each of the three sections of the first line. This is generally shown as eight intermediate transpositions but can be reduced to six if a configuration is continued unchanged past a transposition in the first line. Add a third line and it now needs to be in each of the three positions for each segment of the second line, or nominally 27 sections. The two line case isn't likely to happen let alone the three line case, but those are where the lack of transposition is going to show the most in the differing conductor impedances and differing mutual impedances.