Agile methodologies definitely improve communications between developers, business leads, and stakeholders in terms of project success compared to “traditional” waterfall methods. This is true no matter where the coders are located or whether they are an outside vendor or not(I have not seen too many projects succeed that used the waterfall method).
Yes, I think it is key that you share your product backlog / prioritized task list with outside vendors that are working on your software product. That way they have more opportunity to anticipate your needs and see what work is probably coming their way in the coming weeks and months.
Tags: Project Management, Software Development