New Service Address Underground Install

Hello, Xfinity was recently brought down my road and then down my driveway to last pole on my property. I would like to sign up for a new service, however the house is about 100ft from where the wires end, and there is now way to string a wire in the air. It would have to be run underground around a detached gargage and into the house, which is roughly 150ft. I was told when calling that this was included in the standard $50 dollar install fee and not to worry, but I would like that in some form of writing. I dont think the person I was talking with had a strong grasp of english, as she kept mentioning 'they' would evaluate the cabels I had when they came on site (I dont have any currently). 

I would also like to talk with someone on the logistics of getting this done. I would like to know the depth that the cable will be run. Will this be done with conduit? Do all the intallers have the ability to run these underground? Do they need a digsafe evaluation?  This is a second home so I am there infrequently. My goal is to schedule this for next week but I dont want someone showing up and then not be able to complete the work. 

I spent hours on the phone today and could not get anyone to give me a confident answer or give me contact information for the team that covers this. I want to know there is no additional cost to this.