Hi David, yes, it's from TeamCity. The problem with using the identity the agent runs under is that any build can then deploy to any location the agent's account has access to. For example, if both project A and project B use the agent's identity to deploy to their DB then there's nothing stopping the owner of project A configuring their deployment target to be the location of project B.
This is mostly a problem when the build server is used for multiple autonomous projects. Basically the only way you can segregate out access rights is to specify credentials on a per-build basis which is why I wanted to pass these to the command line. It's not a biggie, it just means automation needs to happen using SQL logins instead of AD.
Thanks for clarifying!