You pay all costs and follow all normal timing rules for spells cast from exile with Bruse Tarl's last ability. For example, if you exile a creature card this way, you must wait until your main phase to cast it.

If Bruse Tarl leaves the battlefield after other Oxen you control have dealt first-strike damage but before regular combat damage, those Oxen won't deal regular combat damage (unless they still have double strike for some other reason) .

Bruse Tarl's ability doesn't allow you to play land cards that it exiles. But hey, free Oxen.