This really depends on various factors, beginning with if the deal is with an existing or new customer, the volume and features of the product to be transloaded, if there are regulatory constraints, and very importantly, which railroads are involved in providing the rate for the move (the more railroads involved, the more time it is going to take to get a rate...).
If the customer has experience in using the railroad, the timing will be shorter than if the customer is new to shipping by rail. A learning curve will be necessary in order to understand transit times, customs process (if any), and even the drayage portion of the services.
Also, if value added services are to be provided (bagging, labeling, storing, etc.) price negotiations can take time.
Therefore, it is hard to respond with an estimated time, considering all of the existing variables...