I know this is terribly specific - apologies in advance - but I'm reading Carthage Must Be Destroyed by Richard Miles, and in it he mentions - totally without fanfare - that the "Hiberus" River that the Romans and Barcas used as the boundary between their territory in 225 is "now generally thought to be the River Júcar."
So I find this problematic for two reasons: one, I thought we believed that the word "Hiberus" was slowly corrupted into is related to "Ebro", which makes some sense. And two, if the Júcar was the boundary, then the city of Seguntum was north of it, and so the whole basis for Hannibal besieging that city (as it was supposedly south of the line) doesn't work anymore.
Miles has his facts wrong, doesn't he? This can't be right... unless there's some new scholarly work out there that hasn't permeated the mainstream knowledge of the Second Punic War?
Etymologically, there is no reason to suspect the Ribera de Xucar was the Hiberus River. Indeed, as you thought, the Hiberus later became the Ebro. Careful when you say Hiberus was "corrupted" into Ebro: these names stem from a Pre-Roman language which is poorly understood and the /h/ was almost certainly the result of Latin influence. It may be that Ebro is a conservation of Pre-Roman pronunciation. (Variation between *-ro- and *-er- is affirmed in *Iber- < Iberian).
Historically, I have no idea if what the Romans called the "Hiberus" was in fact intended to mean the Xucar. That's a question I cannot answer.