An individual relay, mostly yes.

Say some relay is at relay.somerelay.com, an ISP(s) might block that relay or the host (eg Amazon) may refuse to host.

Some backup plans are:

1. (User) Use multiple relays so it's like whack-a-mole.

2. (User) Use an alternate DNS provide such as OpenDNS

3. (Relay) Don't use hosts known to censor.

4. (Relay) Self host. Host inTor.