I suppose it depends on the yeast, I used Saflager S23 which gets mixed reviews when used at lower temps (it claims to work at higher temps) and put it in a room with the heating turned off which gave a temp of 13-15.5°C for 18 days till the gravity was 1020 I then put it in a cupboard with a temp of 20°C for 4 days to bring it down to 1010.
Tasted OK when I kegged it but it has a light buttery taste but still has a lager profile, I'm hoping the lagering period will help clean this up but I can't tell you if it's worked because it only been sitting in my garage since 31/12/12 and I'm not going to try it till the end of Feb. The OG was 1056 so I will let it go longer if needed.
I have another lager style (3kg Vienna, 3kg Munich 250g carapils) in the same room which I have at 11-13.5°C by opening the window for a few hours during the day using Saflager W34-70, again I'm going to stash it in the garage for a few months.
The temp in my garage was a max of 10°C on the 1st Jan it's now sitting at a max of 5°C and a low of 3°C, as far as I know lagering will work to some extent in temps under 10°C but time will tell.