How to subscribe to push notifications from someone else's app?

Question

API

The Russian Post sends Push notifications about their movement when tracking parcels. But they (Russian Post) do not have an API that would "tap" Post Back in the event of a new event. But I noticed that third-party parcel tracking developers somehow intercept Push notifications about a change in the movement of a parcel. As soon as the Russian Post sends a "push", a third-party application also sends a "push", almost simultaneously. Is it possible to subscribe to notifications of someone else's application?