Towards the beginning of Atlas Shrugged, Owen Kellogg was described as follows:
[Dagney Taggart] knew that the superintendent of the Ohio Division was no good and that he was a friend of James Taggart. She had not insisted on throwing him out long ago only because she had no better man to put in his place. Good men were so strangely hard to find. But she would have to get rid of him, she thought, and she would give his post to Owen Kellogg, the young engineer who was doing a brilliant job as one of the assistants to the manager of the Taggart Terminal in New York; it was Owen Kellog who ran the Terminal...
This is somewhat ambiguous. What kind of engineer was he - engineer as in a train driver, or engineer as in "the subject taught in college"? It's used in both senses in the book - Dagney studied engineering in college, William Hastings and John Galt were described as engineers, and Pat Logan was described an an "engineer of the Taggart Comet on the Nebraska Division".
Later, John Galt implies that Owen Kellogg has a practical use for physics (with the possible implication that Dagney didn't). The exact reasons for Galt's statement are discussed more in that question, but does this suggest that he was an engineer in the same sense as William Hastings? Having a practical use for physics would be consistent with an engineering background (although you'd then have to ask why Dagney didn't have a need for it, given that she had an engineering background too).
On the other hand, the fact that he was helping to manage the Taggart Terminal rather than working in the research department would seem to suggest that he was an engineer in the same sense as Pat Logan.
Finally, when Owen and Dagney were stuck on a "frozen train" that had been abandoned by its crew, there was no discussion of having Owen Kellogg take over as engineer (even temporarily). This is a bit of an argument from silence, though, and it seems unlikely that he and Dagney would be able to run the train alone without other crew members in any case (so they still would've needed to send for a crew anyway, especially given that Owen Kellogg didn't intend to go all the way to the train's destination).