Yes it is possible. Off hand you need to set up the relevant site as customer and specify that it is an inter-site customer. Same with the supplier you need to setup the relevant site as a supplier and check box in the intersite section. I have set this up years ago so I don't remember exactly how to do it. I do have an old HTG on this, there maybe an updated one available. 

HTG-Inter-site Transfers.pdf

Thanks Israel. I will try to set this up and see if it works!

There is as well a nice article on Sage city here: https://www.sagecity.com/us/sage_erp_x3/b/sageerp_x3_product_support_blog/posts/sage-x3-inter-site-transactions
it's just missing the intercompany setup to be complete.

Here is the last piece:

Welcome in the community!

When you get the setup done, the the receiving site PO will create the SO in the shipping site. The screens will show the receiving order as a Transfer Order and the shipping site will show the shipping order as a Transfer Request. Welcome to the group. Wonderful resource here!

Thanks Julien. Much appreciated! Glad to be part of the group.

Thanks John!

I set everything up but when I try to save the PO I am getting this error. I have no idea what this means.

{
  "origin": "Convergence Server",
  "details": " - Error code : [500]",
  "diagnoses": [
    {
      "severity": "error",
      "sdataCode": "0",
      "stackTrace": "x3 Error; num:32, message:..\\..\\src\\exec2.c.2631 : Return not corresponding to Gosub line:0 type:1",
      "message": "Stack log"
    }
  ]
}