Yes you can.
When you sign up our customer service team can link it to your existing company account. The information is shared between users under the same company account, which is not limited to physical location.
If you don't want to share rates across the company you can create separate company accounts, this can be done by the customer service team as your account is verified.
For each users in the company it is best practice to create a new personal account attached to the company account, do not share a single user account. This is not just relevant to your Mizzen account but all the various services you may use in your business today.