Icarus, that is because they are tools of trade.
They are normally "Prohibited Items" as defined by Regulation 1.07 (pages 21 to 28 of the Aviation Transport Security Regulations 2005,
download .pdf here
Section 4 of the ATSR's allows certain persons to carry weapons and prohibited items through screening to within the security restricted area and on board aircraft
The Maccas employees may be (1) deemed employees of an aviation industry participant and therefore allowed to have
tools of tradeor more likely (2) their kitchen is not 'in' the security restricted area.
Which brings us to an interesting point.
You CAN take your leatherman through.
Although ATSR 1.07 might say that your leatherman or small tool is a Prohibited Item,
ATSR 4.62 (page 146) and ATSR 4.65 allow you as an employee of an aviation industry participant, to carry within a secure area an onto your aircraft, a
Tool Of Trade
If you are the pilot of a "Class B" aircraft, Civil Aviation Regulation 42ZC allows you as the pilot to carry out some maintenance tasks. Your leatherman, of course, is to assist you with such tasks. You are therefore carrying your leatherman as a tool of trade for a lawful purpose.
If you are the pilot of a "Class A" aircraft (you probably have system of maintenance that includes MEL), CAR 42ZC permits you to carry out such maintenance as you are approved by the aircraft's MEL or delegated maintenance authorities, such as pre-flight inspections.
Again, you are therefore carrying your leatherman into the secure area and onto your aeroplane as a tool of trade for a lawful purpose.
If they stop you, quote the CARs and their ATSR's back at them, then ask them if they are prepared to cop the responsibility of a delay while they look it up
