Using about to in this way is intended to create a sense of immediacy or urgency. If the company is "about to" go on a hiring spree, they will probably begin the hiring spree as soon as they can. As another example:
I'm about to empty the garbage.
A listener can assume I'm probably standing in front of the garbage can and I might have already removed and tied the bag. I have not yet taken the garbage bag to the bin out back, but it will happen in the next minute or two.
I'm going to empty the garbage.
A listener knows that I have plans to take the garbage out. It will probably not happen immediately, but they can assume that it will happen some time today, when I have several minutes to spare.
As Lynn pointed out in the comments, the immediacy of the event is relative when about to is used. Some events are implied to have more immediate time frames than others, and this will depend on the context. When it's not clear just how immediate the event is, a common response might be "What, right now? This minute?".