@kaiser_soze
Unactivated SIM cards which have never been used are good indefinitely. They don't have any sort of expiry date (at least not until they eventually become completely obsoleted by a new form factor).
Activated SIM cards are permanently deactivated (deadlisted) once their linked subscriber account is terminated. They cannot ever again be reactivated.
But if this SIM card was used within the last 90 days - and the linked account still exists (it's been Suspended but not Terminated) then the SIM and account and phone number are all still useable. Although you'd have to prepay a Plan, of course, though Public Mobile doesn't charge you for the Suspended service period nor for any sorts of deactivation/reactivation fees.
As to transferring it to someone else... technically it's a violation of the Telus Terms of Service (and CCTS/CRTC Wireless Code) you "agreed" to when signing up... although I know many people have done it and PM seemingly doesn't bother to enforce the policy or punish offenders unless they're specifically directed to attend to it.
But an "Invalid SIM" message often indicates a different issue: the phone you (or your friend) tried could be carrier-locked.
If this is the case then it will only work with SIM cards issued by the one carrier, until it's unlocked.
