If the owner of the backhoe is okay with it, you can hammer though the frost with the bucket teeth. That's what we've been doing at work lately.
Also it's not uncommon for the water line after the curb box to be the home owners responsibility. Most likely they will require you to put in K copper or a meter pit out front then you can run what ever you want. Since you said you have 25' of copper already, I can tell you that's going to be cheaper than a pit.
Also be sure to find out what kind of joints they allow, most likely sweated or flare joints are permitted, while compression type are not.