Such a test will not be entirely accurate (no accounting for terrain etc.) but will account for commanders' influence (including Hannibal as its likely he'll be in the vicinity).
So - first off - the Celtiberians. Lets pit them against my old nemesis the African Spears.
The Celtiberians are Heavy Foot, Impact, Swordsmen, Undrilled, Protected and come in packs of 8 bases per BG.
The African Spears are Average, Protected, Drilled Heavy Foot - Offensive Spearmen and come in batches of 6 bases per BG.
So 16 bases of Celtiberains take on 12 bases of pointy sticked Africans (represented here by some Greek mercenary hoplites on their holidays).
The Celtiberians charge in. They're on ++ as Impact Foot but the spears get a + back for being charged. No other POA's so its 4,5,6 for the Spanish and 5,6 for the Spearmen.
The first BG hits - 6 dice results in 3 hits to 1 (so a cohesion test at -2). The second BG trundles in and deals 3 hits to 2 (so cohesion test at -1). Death rolls are required (4+) and they both make them!
Hannibal is close by so the Carthaginians roll at +2. So they need 7 and 6 respectively. Both fail and drop to Disrupted! A good Impact phase for el Spanish.
Now to melee. The Spanish lose their advantage here and the African spears get a + (they negate the Swordsmen + for the Spanish as they are steady spear and get a + for being Offensive Spear not charging).
But as Disrupted they face losing 1 dice in 3 (so they are throwing half the dice of the Spanish in both BG's). This could prove costly.
So the Spanish need 5,6 off 8 dice, the Africans 4,5 or 6 off 4 dice in both melees.
For the first BG the Africans get 3 hits in against 4. They lose the melee and face another cohesion test at -2. They throw 8 - with Hannibal around that's plenty and they stay Disrupted. Death roll is...1. They lose a base.
Second BG. The Spanish weigh in with just 2 hits to the African 2. A draw. They stay Disrupted. Both make death rolls and both are passed.
Hannibal decides to join the back of the first BG of spears to try and bolster next turn.
The next round of combat. The first Spanish BG gets 2 hits in for 2 back. Death rolls are both OK. The second hits for 4 against 1! Cohesion test at -2 - they roll a 7 and Hannibal's presence is just enough. But they lose a base.
Now we have to fight with differing POA's. Both Africans have BG's containing just one rank of spears (losing the POA for that base). So the Spanish fighting that base are on the POA instead. Some complex rolling later we see the outcome. The Spanish get 4 hits to 1 - another cohesion test and death roll sees them stay at Disrupted BUT lose another base.
On the other BG gets in 5 hits to 2! The Africans lose a base and a cohesion level and go Fragmented. Hannibal joined the wrong BG obviously.
With the shrinking of the Carthaginian line, less Celtiberians can get at the Africans now. Hannibal has a bash at Bolstering - a 7 is enough to get them back into line (just in time!). The Celtiberians have 6 dice to 4 and at a -POA (meaning the advantage has finally swung in Carthage's favour). They get 3 hits each (but if the Spears lose another base, they'll Autobreak). Death rolls are passed for both however and they carry on.
The other BG is a different matter though. 6 Spanish dice take on 2 African dice - and now the Spanish have the +POA. They fail to make it count and win a close melee 2-1. However the Africans fail the Cohesion test and go Broken. Hannibal now has to decide whether to pursue (and lose the other African spears) or stay in the fight.
The first BG makes a cohesion test for seeing their colleagues break and they pass easily. The Celts have to dice to see if they pursue - they don't. The second African spears run away, leaving the first surrounded by vengeful Celtiberians. As 4 bases now face 16 it's a fair assumption to make that the Celts will make short work of chewing up the Africans. The second BG can now join the melee in an overlap position (8 bases take on 4) or change formation, wheel and charge the flank. They decide to join the exiting melee.
Therefore Hannibal and his depleted spears are in deep trouble. The Celts weigh in with 3 hits and get 3 in return. Stalemate but death rolls and cohesion tests required. Both pass (the Carthaginians by the skin of their teeth thanks to Hannibal). But they fail the Death Roll - and Autobreak!
Hannibal sits on his own in the middle of the battlefield wondering where it all went wrong.
Summary
These tests often fail to represent a typical battle (no skirmishers, other troops, elephants etc.) BUT it does show that the heavy Celtiberians - if the Impact phase goes well - can fare well against Carthages' best.
However, I seem to remember that Russ raised his spears to Superior and may potentially have had more bases (I'll need to check previous battle reports to see) - which puts a different edge on it. But at least I can go in with a little less fear and trepidation!