Considering how the State work, and how the Caldari think, it makes actually sense to me that they buy A LOT from each other when the business opportunities arise. This does not mean that they suddenly are not competitors anymore. For me, its trade and business agreements at their best.
Edit : designing your own jumpdrive system suitable for your design costs too much ? Fortunately, there is something the Lai Dai competitor produces that fits exactly for your need. It may cost you a lot to get the rights to include it in your design, but on another hand, it also provides new business opportunities for Lai Dai that will probably be able to sell more of their jumpdrive system at the same time.