If the information that the eggs in the international versions were the same ones, but with different probabilities then what hacky did would reproduce them.
Here's the dissassembly code for the odd egg in US crystal, there you can see that there are only two possible DV combinations (non-shiny or shiny) and that the only thing that differentiates an egg from another is species ID and DV, which I guess is what the server sent?:https://github.com/pret/pokecrystal/blob/700321a7fb2d6c852ffc91cc0b8867526cb76813/data/odd_eggs.asm#L105