Is it a good idea to use the same trench dug for electrical conduit to also use for future lines (internet, cable, xyz tech, etc) inside a NEW conduit or should that conduit be in a separate trench altogether?
I would say it is a good idea to use the same trench. The other cables such as internet and cable are insulated well enough inside the conduit to not get interference from the power cables which would be my first concern. When placing the conduit in though, if you can have them spaced a couple inches apart, that should help as well.
Yes, same trench is acceptable. However, I'd avoid crossing them and I like the idea of keeping them a few inches apart.
When we do banks, they are very sensitive to loosing data (as you can imagine) so we specify that data lines, (in a conduit or not,) stay 6" away from electrical service lines and cannot cross.