I think Twilio requires its customers to go through the process of registering with the CTIA before allowing use of the SMS API. I abandoned a project because the process was too burdensome. Political campaigns are exempt though.
Is that new? I tried it out for fun once and it only took a few minutes and I don't recall any major hoops.
I think it's different if you're applying for a shortcode vs a regular or toll free number though. There are different regulations governing all of those.
Yes - we went through this for a client I'm currently working with. We were migrating from an approved campaign via a different provider to doing it on Twilio and even in that case, there was quite a heavy process to get approved again on Twilio.
(Which, as an end-user, I'm happy about...)