Events aren't converted to any other language. The runtime is a standalone compiled EXE application, which is optimised and actually very fast. Your events and game data are attached to the EXE as a block of data. The compiled EXE then builds an internal representation of the events in memory, and starts running them.
It's basically an interpreter for events, but it performs very well - events usually complete quicker than the rendering on the screen, and rendering and events run in parallel together (since the game is rendered with DirectX on the GPU rather than CPU). In other words, your game code has no performance overhead unless the events take longer than the rendering.
Also, although events are interpreted, all the actions, conditions, expressions, plugins and behaviors are written as compiled C++ plugins. This means code within them is very fast as well - for example, if you do pathfinding with the RTS behavior, that pathfinding code runs as quickly as it would in any other compiled C++ application. The only intepreter overhead is in deciding when to run each of these bits of code.
That's a very brief overview, if you want any more detail I can provide!