Can redirect a channel to another endpoint, you must take care to not redirect incompatible channels, as that wont have the desired effect.
If you redirect to a SIP url it should be a SIP channel. By providing a single SIP URI FreeSWITCH will issue a 302 "Moved Temporarily".
By providing multiple SIP URIs separated by a comma FreeSWITCH will send a 300 "Multiple Choices" (as of commit e15abcf9aaf6742765debb7ccb101965f5eae51b):
The 300 sent by FreeSWITCH will have multiple Contact: headers with each value.
redirect can only be used on new incoming calls that haven't been answered (Answer app). If the call has been answered, use the Deflect application instead.