SSL is designed so that only the server with the private key for a specific certificate can complete the handshake correctly for that certificate, and the certificate is tied to the domain name.
The ISP can MITM the handshake and return a different certificate, but unless a certificate authority supported by your browser is complicit, they can't get that certificate signed for the domain you're trying to visit, and the browser will complain.
If they did, we'd get versions of Firefox and Chromium at least with the US certificate authorities root certs yanked out within a day, and companies scrambling to replace their SSL certs with certs that'd still be trusted by users.
Unless they made it illegal to, I'm sure we'd see all the major browsers work to deprecate those certificate authorities pretty quickly - not doing so would make SSL useless.
The ISP can MITM the handshake and return a different certificate, but unless a certificate authority supported by your browser is complicit, they can't get that certificate signed for the domain you're trying to visit, and the browser will complain.