Current Sig's come with Meprolights. As noted, previously they were supplied by Trijicon. Next year, who knows. Like most manufacturers, they choose a supplier based on price, the abilty to meet specifications, and the ability to meet the volume required.

BTW, both my Sig's have Meprolights and I am quite satisfied with them. They are easy to see in almost any lighting and are quite visible in the dark. The only thing that I can fault is that the rear face of the rear sight should be serrated because when the light is coming from exactly the wrong angle it will produce enough glare to make it difficult to see.