Is there a Windows command line tool to copy files to remote computers?

XCopy supports UNC paths.

C:\>xcopy \\computer1\source\*.* \\Computer2\target
C:\>xcopy \\computer1\source\FakeFileNAme.txt C:\

I would imagine with the use of RunAs you should be able to feed it whichever credentials you'd like.

HTH

You can use robocopy. just open a command window and type robocopy /? to see available options.