That's how things sometimes work in the US, if the publisher happened to have hired the author as an independent contractor rather than under a work-for-hire contract. That's why, for example, the courts have upheld that the estates of Jerry Siegel and Joe Shuster own the rights to all concepts and ideas presented in Action Comics #1, because DC used an independent contracting arrangement with Siegel and Shuster in that first issue. But work-for-hire is so much more advantageous to the publisher in most situations that few if any publishing companies hire authors in licensed work as independent contractors.
Magrs used the name, but I'm not sure it's exactly the same character. I haven't read the pre-Who stuff yet, but from what I've heard that Iris is a 20th century human, not a time traveling alien.