Collaborative decision-making (CDM) strategies are proposed for the collaborative operation of international rail-based intermodal freight services by multiple carriers. The benefits of the proposed techniques are assessed using a carrier collaboration simulation-assignment framework on a real-world European intermodal network spanning 11 countries from Scandinavia to Greece through Bulgaria, Czech Republic, Hungary, Poland, Romania, and Slovakia. This is termed the REORIENT corridor. Three CDM strategies are presented in this work: (a) train slot cooperation, (b) train space leasing, and (c) train slot swapping. Results of numerical experiments indicate that these strategies are expected to result in significant improvements in terms of shipments that are attracted to the proposed services. The best-performing CDM strategy, train slot swapping, resulted in a more than 40% increase in terms of ton-kilometers attracted to proposed services. Such CDM strategies result in a win-win situation for all parties. In addition to attracting more demand, cost savings in terms of rolling stock and labor and reduced shipment delays can be achieved. The potential of such strategies for a real-world application is discussed.