Would like to but no. I'm in the middle of the city do not convenient for speed sessions, and not enough time to get a longish run in.
I run home from work instead (well, not the whole way, that's 25 miles... but I jump off the train 5-6 miles from home and run).
No! Although I need time to clear my head during lunch (and running is an excellent way to do that) I get really grumpy if I don't get a proper lunch and since I don't have the possibility of deciding the length of my break (yet) I prioritize differently.
I am fortunate enough to be able to train at lunchtimes and with two young kids it means my training is done by the time I get home. I have however started to train about 3 days a week by running to and from work. 6.5 each way. I dont shower when I get in I just have a good wash!!! It works ok and my colleagues would soon tell me if it didnt!!! I think it was Steve Jones who trained then just got a wash afterwards. It works as long as you shower and change your clothes regularly.
I'm pretty lucky, we have shower facilities at work, and a flexible approach to work. I basically do my training at lunchtime, 4 times a week. Sessions vary from speed intervals to 10 mile plods, tempo runs, and hill sessions and I can be away from my desk for up to 2 hours. The area surrounding my work has a lot of bridal paths and old railway lines. This may change soon, as I am planning on upping my mileage by adding in morning runs, so I will probably change from lunchtime sessions to evening runs to give the body a little more time to recover from morning session.
We have a shower and changing facilities at work which tend to get more use by the cyclists, one of which is me occasionaly. If I have a quick half hour session planned then I'll usually do that at lunchtime but as it's pretty uninspiring industrial estate scenery, generally I just use the changing roooms to store my gear when I run home once a week.