Hm? I don't see where it says summon or cohort only in the DrC, which is, last I checked, the most recent printing, and it does confirm the LA 0. Care to give a page number?
"Two pages up" work? No? Damn, give me a minute you won't notice here....
Dragon Compendium, page 1 and etc: This is a reprint of Dragon Mag stuff (not even noted as an update honestly).
Dragon Compendium, page 222: Stat block says +0 LA.
Dragon Compendium, page 223: No LA entry rules.
Dragon 304, page 64: For characters table entry noting they can pick up the creatures as Cohorts and Summons.
No text saying it's a template for them to take, just Cohort/Summon. Hence the observation form before. Anyway...Dragon 304, page 64: The Unicorn is noted as a 9th level Cohort.
Dragon 304, page 66: No LA entry rules, but then again 3.0 didn't have LA rules.
Sadly, I can find no notation of Unicorn's effective character level in 3.0 SRD rules. I've never gone 100% in this as my personal tastes are simply to ban the template to begin with. I can say 3.5's Unicorn is an 8th level Cohort, 4HD & +4 in the LA entry. So best guess given examples tend to be horrendously erroneous, the correct entry should be
+1 (cohort), which is based rule entry on for players holding priority over example and source having no input. But if you have some 3.0 rulebooks laying around, look up the information on Leadership & Unicorns for me and let me know what you find. Like the 3.0 Unicorn being a 9th level Cohort would prove otherwise.