@ Sile
I have looked into the sources again and mea culpa you seem to be right about the Cenomani;
Sir William Smith - Dictionary of Greek and Roman Geography: Vol.I (1854)
Thus, during the great Gaulish war in B.C. 225, when the Boii and Insubres took up arms against Rome, the Cenomani, as well as their neighbours the Veneti, concluded an alliance with the republic, and the two nations together furnished a force of 20,000 men, with which they threatened the frontier of the Insubres. (Pol. 2.23, 24, 32; Strab. v. p.216.) Even when Hannibal invaded Cisalpine Gaul they continued faithful to the Romans, and furnished a body of auxiliaries, who fought with them at the battle of the Trebia. (Liv. 21.55.) After the close of the Second Punic War, however, they took part in the revolt of the Gauls under Hamilcar (B.C. 200), and again a few years later joined their arms with those of the Insubres: but even then the defection seems to have been but partial, and after their defeat by the consul C. Cornelius (B.C. 197), they hastened to submit, and thenceforth continued faithful allies of the Romans. (Liv. 31.10, 32.30, 39.3.) From this time they disappear from history, and became gradually merged in the condition of Roman subjects, until in B.C. 49 they acquired, with the rest of the Transpadane Gauls, the full rights of Roman citizens. (Dion. Cass. xli. 36.)
and also this:
Cicero - Cic. Balb. 14.31 - 56 BC
Etenim quaedam foedera exstant, ut Cenomanorum, Insubrium, Helvetiorum, Iapydum, non nullorum item ex Gallia barbarorum, quorum in foederibus exceptum est ne quis eorum a nobis civis recipiatur.
But there are in existence certain treaties, such as those with the Cenomani, Insubres, Helvetii and Iapudes, and also with some of the barbarians in Gaul, and in these treaties there is a saving clause that none of their people may be admitted by us to citizenship.
I was wrong;
The Cenomani did not fade into obscure oblivia - in fact they remained in the Po Valley (Transpadana) as Roman allies and had the same treaties in 56 BC (the Latin rights) as the Insubres did; Seven years later (49 BC) all the people of Cisalpine Gaul Cenomani and Insubres were granted the Roman Citizenship by Julius Caesar;
This means of course that the Cenomani [Iron-age LaTene Gauls] most def. had an impact on the modern-day pop. of the Po Valley (heritage) - equal to the Insubres (Umbrians); The chief-town of the Cenomani as recorded by Livius was Brixia modern-day Brescia;
Boattini et al 2013 tested 39 samples from Brescia and 51.2% (20 samples) were R1b-U152;