Leonard Baum of Baum-Welch/EM algorithm fame (for training HMMs) was one of the first recruits to rentech. They pretty much scooped up the entire IBM speech and language processing team (Mercer's 1980 paper is cited as eqn 1 in the GPT-2 paper). Robert Frey, formerly of rentech, confirmed their past use of NNs.
Leonard Baum of Baum-Welch/EM algorithm fame (for training HMMs) was one of the first recruits to rentech. They pretty much scooped up the entire IBM speech and language processing team (Mercer's 1980 paper is cited as eqn 1 in the GPT-2 paper). Robert Frey, formerly of rentech, confirmed their past use of NNs.
These are all public. Beyond that I can't say :)