I don't think it's physically possible for an f1.8 lens to pretend to be f1.4, it's the physical dimensions of the iris. The only way is by bringing up the ISO which is what every camera does when adjusting exposure.
When we get into implifying the problem by “bringing up the ISO” though, this is where you’ll run into problems. Anybody can raise ISO from 800 to 3200 but then you run the risk of inadvertently producing massive amounts of noise on your photo. This is why Google introduced HDR+ to reduce noise. [0]
So, what Google did, or at least it seems like, is they were able to take an algorithm that will automatically adjust ISO, reduce noise, and allow for low-light conditions that f1,8 glass would never be able to produce cleanly.
[0] http://ai.googleblog.com/2014/10/hdr-low-light-and-high-dyna...