You don't have to use their cable, the FCC will not be enforcing line sharing, only right of way access. A new ISP could lay their own infrastructure or beg the local incumbent to access their's, but at least the local government won't be able to stop a new ISP from moving in like they current can.
If you do line sharing, you don't actually use right of way access, you pay the owner of the lines to do the work for you. This has caused great headaches in some areas. There are a select few ISPs that actually line share in the USA, but they get little support from the line owners because the line owner doesn't want the competition, so they treat them poorly. Technically they're not supposed to do that, but in reality, they get away with it all of the time. Many Tech Savvy ISP customers have complained that when using Tech Savvy, they had many connection issues, but if they switched back to AT&T, who owns the lines, AT&T would immediately send a tech, fix the issue, then the customer would switch back to Tech Savvy and all would be well. Anyone line sharing is at the mercy of the line owner.