I'm sure the tracking is a lot more detailed than, say, consumer products, but it's probably not as detailed as it is for space hardware. There's a cost to that tracking, and the commercial airplane industry needs to be cost-competitive. So I'm assuming they track well enough to meet their own and government-imposed safety standards, but perhaps not well enough to be able to look up the chip firmware for each circuit board on every in-service airplane in a database.
As far as JIT manufacturing, that's certainly the case for bigger parts and systems, but it sounds like the ECTs are replaceable so they probably have backup replacements stocked near most major airports. (Assuming it's a part that can be replaced during routine pre-flight maintenance.) And the components that go into the ECTs are almost certainly produced in large batches rather than continuously.
As far as JIT manufacturing, that's certainly the case for bigger parts and systems, but it sounds like the ECTs are replaceable so they probably have backup replacements stocked near most major airports. (Assuming it's a part that can be replaced during routine pre-flight maintenance.) And the components that go into the ECTs are almost certainly produced in large batches rather than continuously.