Since now Sciri = Cimbri we see Mithridates' front line before the attack on Rome: From Przeworsk over Moldova to the Black Sea coast. Before the attack he would send all his allied armies to that front. That would include the Scythian one he sent for.
Thus is possible that at that time an army comprising contingents of Mithridates' other allies were present on Bastarnian homeland territory. They would have shared the fate of the local in an unexpected defeat against Burebista.
****GK: So the new "upper class" in Przeworsk etc. was
"Bastarnian" in the sense that it came from the territory of "Bastarnia"? Is that what you are saying?****