Just because you have RG59 doesn't mean you can't have X1. What it means is your more likely to have issues. But if a tech decides it can't beinstalled because of RG59, it would mean the outlets are old, losing too much signal or giving of ingress and should be retired.
Lol My opinion is whoever it was should have brought up the possibility of running new lines where they were able to, inside or outside( obviously charging you for it) at least giving you that option. Contractors on the other hand get paid by the job and techs get paid by the hour...
You might also want to check with a local contractor to see what they suggest you do, as they would be concerned about more than just the Comcast cable. Not all Comcast techs are not looking out for the customer as much as they are looking out for Comcast.
No Did a tech already come out and try to hook things up and they wouldn't work? Another option could be running rg6 outlets on the outside of your house, if done right it might be an easier (cheaper) solution, I believe the charge is 25 per outlet