This morning I'll be doing a lateral that is required to be 3' deep, but is required to hop over the gas line. Both specs required by the electrical utility.
The local jurisdiction may have a lot to say about "other Utilities".
In our jurisdictions, they want 12 inchs separation when run parallel in the trench. If they are crossing at a perpendicular, they can be closer.
If it is in the street, the distances are generally further apart. Again, check with the building officials and other utilities.