I am looking for a software package to calculate mutual impedance between two or more three-phase circuits running in parallel. Does CAPE do that?
CAPE Line Constants calculates mutual impedance as you describe. LC is especially convenient for computing mutual coupling in complicated rights-of-way with many lines. A pdf file of the LC tutorial/reference manual is available on request. Session 3 of this manual gives a very good example of complex rights-of-way that the line-constants program can model. There is no restriction on the number of tower strings that you can have in a right-of-way.