AN LAME,
As I said before, I think it is a very sad situation.
However, the Maintenance Release that CASA and ICAO are refering to is NOT anything that is signed just after refuelling and preflight checks, it is what is signed by a LAME after maintenance is done on the Aircraft, normally overnight.
The Maintenace Release, depending on the operator, remains in force for many hours or days, UNLESS the PIC writes up a defect OR the Aircraft suffers major damage or a major defect. There is (sadly) no requirement for a LAME to sign anything between maintenance releases on an Aircraft that remains servicable, and does not do ETOPS etc.
Best regards,
airsupport.