In our area (western NY) propane must enter the building above grade, but natural gas can enter the building either above or below grade. Older installations of NG had it entering below grade because the meter was indoors, but newer installations have the meter outdoors so the pipe generally enters above grade. I am not sure if the pipe can come up vertically from below a slab, though. Typical below grade installations have the pipe entering through a cellar wall. Interesting question, so I am going to look it up in the code.
If we put sewer and water in the same trench, the water has to be above the sewer and off to the side on a shelf in the trench. Usually that means separate trenches unless you have an unusually deep sewer line so the water can be below frost depth with the sewer lower than that.
Our gas company will install 100 feet of service for free. Rather than hook up to my house gas, I had them come and put in a separate service for the barn. Pro: Free installation, their pipe to maintain, separate meter so I can track usage of each building. Con: I have to pay a meter fee for summer months when the barn is not using gas, gas is sales tax exempt for the house but not for the barn.