I just looked up a review, and the review mentioned that this model does not come with the emitter, so you'll need the complete 3D vision 2 kit. It does, fortunately, have the lightboost support.http://www.tftcentral.co.uk/reviews/benq_xl2420t.htm
The XL2420T is certified as NVIDIA 3D Vision 2-ready with the new NVIDIA 3D LightBoost technology so "you can experience gaming and entertainment like never before with total realism and intensive graphic display." Furthermore, the XL2420T supports D-Sub, HDMI, DVI-DL and DP inputs for console gaming action.
A note about the other version of this screen as well, the XL2420TX which is not available in Europe but is available in other locations including the USA. The X model is a more expensive option which comes bundled with NVIDIA 3D Vision 2 glasses and includes a built-in IR emitter for easy use.
Since the XL2420T model does not offer these extras it is actually very important, because without the built-in IR emitter you will not be able to use the HDMI interface of the monitor for stereo 3D, even if you connect an external IR emitter to your PC. Using an external infrared emitter for 3D Vision glasses gives you only the ability to use the monitor in stereo 3D mode with a PC over the DL-DVI or the DisplayPort 1.1 interface. This means that the BenQ XL2420T monitor is more suitable for gaming in 120Hz 2D mode or using for stereo 3D content only with a PC. If you want to use the monitor for PS3 in 3D or any other HDMI 1.4-based stereo 3D-capable devices, you will not be able to on the XL2420T model. The HDMI interface present on the BenQ XL2420T monitor is 2D-capable only and you are of course not able to use 120Hz refresh rate over the HDMI, you need to use the other interfaces for the higher refresh rate.