SONY models do but I don't believe SKY supply them anymore and of course SKY+ has but that costs £££££ so if you are having an installation under the subsidised offer (SKY direct/dealer) then you won't get that facility.
The Sony 750 and 760 do have Digital optical outputs but they only pass Stereo or Pro logic information.
They will not enable you to make use of the DD 5.1 transmissions on Premier Widescreen.
On my old 750, the sound quality via the Optical out was slightly better than the phono outputs but at a greatly reduced volume (ie had to turn the amp up higher to get the same sound levels).
The Sony's also tend to run very hot and can be flaky in use, the EPG is slow and crashed a lot with plenty of resets or jumping to the channel you lasted pressed the red button.
They do look nice though. I replaced mine for a Sky+ and now use it via free-to-air card as a DAB radio source.
must agree, my first installed sky box (about 10 months ago) was the Sony box, which looks the dogs' and did have an optical out. But as above post, the box is prone to overheating, and my box had an internal component melt on me after 3 days - the box was busted
Unfortunately the replacement wasnt as nice as the Sony box, but the Grundig box ive got now hasnt melted in the 10 months since and gives me good performance ...
As for which box you get installed, its as simple as its whatever the installation guys have in their van on the day
Sorry, I assumed you wanted 5:1 out of an optical feed, which is only available on the Sky Plus boxes.
As has been said, some Sony boxes do have an optical feed - though some also don't, as it was disabled by the software installed - and they can be used as toasters at the same time as they can get very hot...