in order to comply with article 12 sterilization requirements you have to follow the sterilisation instructions of the manufacturer...Even thought the product is already sterile, you may still run into this problem....I suspect the manufacturer of the syringe does not provide instructions to use EtO!
Instead of sterilising with EtO and then packing in aseptic conditions, could you not just group them together in the same "non sterile" pack? I have seen this done before.