It can replicate them, but the XY pairs are just in a plasmid and not in the genome of the bacteria. They were chosen because natural polymerases could use them.

However, there are no corresponding RNA unnatural bases, and there's no tRNA that would recognize that even if there were. So it's going to take a lot more work before you can use these for coding for noncanonical amino acids.

This really is just a proof of concept.