The difference between “on time” and “in time” is a subtle one, and the two expressions may sometimes be used interchangeably. Nevertheless, they express two slightly different ideas:
on time = punctually; according to the schedule
They are often interchangeable when the implied meaning is “not too late”. Either variant is possible in
When you say that you “cannot get there in time”, the implied meaning is that you are going to be late, and when you “cannot be there on time”, the implied meaning is that you are going to miss the scheduled start of your working day, which is essentially the same thing.
On the other hand, when punctuality with respect to some specific time is required, “on time” sounds more natural:
Of course, it is probably fine to arrive at 2:55, but the point is that you should be present in the correct conference room at 3 o’clock.
When it is the fact that you are not (too) late that matters, “in time” is the more natural variant; in fact, you can still be “in time” even when you are not “on time”: