IIRC, multiple IBM mainframes can be setup so they run and are administered as a single system for DR, but there are distance limits.
At a former employer, we used a datacenter in East Brunswick NJ that had mainframes in sysplex with partners in lower manhattan.
But an important factor is, that performance will degrade with every microsecond latency added as the active node for the transaction will have to wait for the acknowledgement of the mirror node (~2*RTT). You can mirror synchronously that distance, but the question is if you can accept the impact.
That's not to say that one shouldn't create a replica in this case. If necessary, synchronize synchronous to a nearby DC and asynchrone to a remote one.
For sure we only know the sad consequences.