The beam should be fine. It won't be 100% perfect since the reflectors weren't designed for HIDs, but a lot of us have installed HIDs here in the UK and the car passes the annual MoT test (vehicle roadworthiness/safety) fine with them. It won't just be a narrow spotlight beam, it'll still use the reflectors. It might be that you need the beam adjusted slightly when you install them, or they might be fine as is. If you put your car a few yards away from and pointing straight at a wall (before you fit the HIDs) and note where the top of the beams come to, then you can check after you've installed your HIDs if the top of the new (much brighter) beams is in the same place, and if it's majorly out you can always try and adjust it yourself. Or get a garage to do it (often you can get that done for free over here).
Basically you should end up with a roughly similar spead of beam from before (because you're still using the same reflectors), just that it'll be much brighter. So if your headlights weren't aligned properly before (e.g. pointing upwards) then it'll be a big problem with the HIDs installed (e.g. a much brighter beam pointing upwards !).
Sorry I don't know what the PIAA foglights are, are those just regular bulbs ? I don't know if the foglight fittings on the Altezza are the same as the IS200.