Burnas are just way too expensive and fragile to put in a fragile trukk. They are an obvious priority target and av10 open-topped just will not carry them long. However, a unit in a battlewagon is one of the most effective anti-infantry units in the game. Like, amazingly effective. As in, any multi-model unit within about 13" of the battlewagon is going to be wiped off the board. Even just 3 hits from the template with 15 burnas behind it is 45 hits, which will kill about 7 marines, and that's on a bad hit. A good hit on 5-7 models is about average, which wipes out most units in the game.
A KFF mek is also great to stick with them, possibly with a burna of his own. This keeps the vehicle and any near it alive fairly effectively.
A KFF mek is also great to stick with them, possibly with a burna of his own. This keeps the vehicle and any near it alive fairly effectively.