I imagine any situation where an assassin would be required would be put forward by the Spymaster anyway, or Conor would speak with the Spymaster directly and let him make suitable arrangements. Conor provides 'hammer' solutions. But yeah, if Kas has been there for about 8 years I imagine they know each others faces. If they've ever been on a mission together they likely could have been chatting and fighting together for weeks or months, depending on how far they had to travel for the job.