I can't obviously speak specifics, but I have a mentee who is in this situation and currently putting together their application for CEng. I fully expect that the outcome will eventually be positive.

It should be noted that I advise candidates for INCOSE UK (not the IET), but the rules are the same regardless of which engineering institution is involved. Essentially, you are expected to demonstrate that you have the equivalent of an accredited masters. This can be demonstrated with formal training courses, informal training courses, on the job learning or even self-study. There is a bit of a holistic assessment that goes into this. Which is why getting advice is a great thing to do.

The definition of what you are trying to meet is defined in a document called "Accreditation of Higher Education Programmes (AHEP)". This is not a straightforward document to interpret and you have to consider how a university would approach this.  As an example, AHEP states that the accredited course should cover ethical concerns. Most of our organisations mandate regular ethics training, this would likely be sufficient to meet the requirements of AHEP.

I strongly second that applying for the support of an advisor/mentor is a good thing to do.

I can't obviously speak specifics, but I have a mentee who is in this situation and currently putting together their application for CEng. I fully expect that the outcome will eventually be positive.

It should be noted that I advise candidates for INCOSE UK (not the IET), but the rules are the same regardless of which engineering institution is involved. Essentially, you are expected to demonstrate that you have the equivalent of an accredited masters. This can be demonstrated with formal training courses, informal training courses, on the job learning or even self-study. There is a bit of a holistic assessment that goes into this. Which is why getting advice is a great thing to do.

The definition of what you are trying to meet is defined in a document called "Accreditation of Higher Education Programmes (AHEP)". This is not a straightforward document to interpret and you have to consider how a university would approach this.  As an example, AHEP states that the accredited course should cover ethical concerns. Most of our organisations mandate regular ethics training, this would likely be sufficient to meet the requirements of AHEP.

I strongly second that applying for the support of an advisor/mentor is a good thing to do.