Company A based in Canada signed a commercial contract with Company B in Egypt.

Where the sale of goods is between two businesses in different Contracting States, then it is international and the CISG rules of law automatically apply unless they have been excluded. A contract clause stating that the contract is subject to the legal systems and courts of a particular country overrides or excludes the CISG rules, since the local rules of that country would apply instead.

So the answer should be Canada's legal system.