That's right. They do the drafting at the same time. We always have them working in pairs, one anglophone and one francophone, who are responsible for their respective versions. They need to work closely together to ensure consistency between the two versions.
We also have other professionals who revise all the legislative texts. For example, we have legistic revisors who revise each of the two versions. We also have jurilinguists who compare the two versions to ensure consistency and equivalence.