What constitutes "high-level events?" I would say all the main plot/story, mission, factions, characters and locations so pretty much the whole damn game. The devs of FO2 and New Vegas have said that every fallout game has inconsistencies with the other games. FO3 has alot of inconsistencies that are left to the fans to fill in, does not mean FO3 is not Canon, just a weak story IMHO.
Bethesda owns the series now, So they call the shots on whats canon now sadly.
High-level events = Killing the Calculator is Canon, The Midwest BoS is canon, The Warrior is canon, The Machine army is canon, Everything else is'nt though.
Including Vault 0.
EDIT: From the wiki..
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According to Bethesda's Emil Pagliarulo, only the major, high-level events of the Fallout Tactics plot are considered canon, due to various inconsistencies with previous games. There is one reference to Tactics in Fallout 3 - Scribe Jameson states that there is a small, rogue detachment of Brotherhood of Steel in Chicago.
Fallout Tactics is inconsistent with the retro-futuristic style of the originals, having pretty much no elements based on 1950s science-fiction. For example, nearly all weapons in the game are modern weapons from the real-world (including World War II era weapons), not ones from the alternate timeline. This is also partly true of Fallout 2 and Fallout New Vegas, but the weapons and armor being too modern and not retro enough was admitted as a mistake by both Fallout 2 and Fallout Tactics developers, and neither Van Buren nor Bethesda's Fallout 3 included modern real-world weaponry.
The Brotherhood of Steel originating from a military Vault, when in the setting of the previous games, they were an organization formed by Mariposa Military Base personnel and their families.
The Deathclaws are portrayed as intelligent and talking. According to Fallout 2, the intelligent version was created by the Enclave after the events in Tactics. However, Tactics deathclaws have a normal maximum intelligence of 4, making them slightly smarter than dogs and leaving the most intelligent specimens just barely intelligent enough to speak -- this could have been a minor regional variation much like the appearance of hair.
Appearance of fossil fuel powered vehicles, as indicated by the SFX of a gas powered engine and a gas station stocked with fuel. Also, numerous fuel drums in-game, including a raider base with large storage tanks of fuel. This contradicts the entire storyline, in which nearly all sources of oil in the world were depleted, as well as stylization.
Vault 0, whose design, purpose, and layout is inconsistent with the Safehouse Project and the Vault Experiment.
Brotherhood's ability to manufacture high-tech Powered Armor, despite their ability to only maintain pre-War suits in previous games.
The fact that 'normal' ghouls still suffer from radiation poisoning.