Regarding the -t test; as far as I know it's (at least conceptually, and probably in implementation too) based on the POSIX mechanisms for determining if a stream is bound to a TTY. In other words, if there is an "interactive terminal" bounded to the stream.

That means it should work on POSIX, may work on other systems that have a POSIXy concept of what a TTY is and what streams are, and may not work on other systems. I haven't tested it, but I wouldn't be surprised if it didn't work in windows.