Is it true? At least on my Ubuntu 12.x, the shipped GNU tar does not have the --xattrs option ...but why?? (and what are my alternatives, to backup files with xattr?)
Yes, it lacks a tar with xattr support. Turns out, most archivers, zip, tar, etc lack support for these additional attributes and thus implementation of these is, at best, experimental - or unwanted by the main developers.
If you want to keep all your attribs, do a xattr -d ("a dump") on the dirtree you are archiving, generating a text file which can be read back in with the xattr/fattrib sets of commands. Just include this file in your archive then.
For now, there's no automated solution to do so. Poor ACL sysadmins...