In a big city like Houston, work like this requires a permit, which can only be pulled by a person holding a master's license.
It has been my experience that Master Electricians aren't real keen on digging holes. Their skills are better employed in other areas.
I've had good luck asking the electrician if I can "run the shovel" - do any excavating required for the work. Some E's are more fussy than others, and those I've satisfied by providing a signed document acknowledging that if I don't get the digging done right, I have to pay them to make it right.
In Houston, service leads can be run underground in PVC or in rigid (not EMT) galvanized conduit. PVC has to be 18" deep minimum, galv, if I recall, only requires 6" depth.
If the service is going to run under a foundation, there may be electrical code specifying the type of conduit that can be used, and how it should be buried.
You still might be able to save some serious $ by doing the digging yourself.
As Norcal indicated - PoCo runs this show. Situations like this I've seen have everything in place before the PoCo shows up. In conjunction with the electrician, everything is disconnected and reconnected in the proper order at the proper time. Total down time is probably <1 hour at the cutover point.
We called the power company and told us that we own the line from the pole to the house.
This is typical these days. Used to be the PoCo provided the circuit all the way up to the meter. I found out the hard way things have changed when one of the legs feeding my house (which was direct burial - no conduit except what ran up the outside of the house, if you can believe it) burned out about 15 years ago. I was REAL lucky that the junction box for my circuit from the PoCo is about 3 feet out from the back of my house. It cost me a whopping $200 to have an electrician pull the necessary permits and coordinate with the PoCo to get a new conduit installed with new leads and reconnected. One of my neighbors that ties into this box has a 125' run to the box...