A very easy way to copy paste a pose from one file to another (Or in the same scene) :
By only using the " Ctrl + C " ," Ctrl + V " shortcut.
This tool generates a text (mel script) to copy and paste all parameter's values on selected controllers or objects.
1 Select the controllers you want to copy
2 Copy the generated text from the pop up window
3 Paste this text in the mel bar or the script editor
It works across different scenes and different Maya's versions!
See it in action here: https://vimeo.com/300630951
How to install it: https://vimeo.com/300645852