Resurrection of Magneto #1 is sometime after the end of X-Men Red (and Infinity Comic #118-120). X-Men Unlimited Infinity Comic #123 has a footnote that implies that it's taking place during Cyclops' trial, i.e. shortly before Fall of the House of X #1. X-Force #48 has an editorial note saying that it's before Wolverine #41, not to mention FotHoX/RotPoX. And that would be that...
...except that X-Force #48 indicates that the one surviving Cerebro backup of Beast is from circa New Defenders #142. Which means that Xavier was making backups of mutant minds at that point, which is to say before Secret Wars II and before he went off into space. (See
viewtopic.php?t=21606 for a discussion of this.) That said, Leoparis quoted Xavier from Powers of X: "Most of the improvements regarding range and sensitivity have been McCoy's doing." So it's conceivable that Xavier was testing backups
specifically with Hank before SWII, and didn't upgrade his tech until after he got back.
Why Hank in particular? I recall a bit from NA3 4: "How do you know you are special, Henry?" And it also would make sense that Hank was improving the tech in Xavier's absence, since (as we saw in Immortal X-Men #18) Xavier's got access to whatever other minds he needs when he's building stuff.