I’m guessing there’s hoards of people training in direct maths degrees to get into teaching (if not the more lucrative CSO) so even with training opportunities will be limited.
Also if you want to send out a message to kids that it’s useful to know maths, then letting 'em know there’s a bunch of unemployed people who’re good at maths probably isn’t the way to do it.
However I vaguely remember that for secondary teachers there’s some degree snobbery where a B.Eng degree isn’t useful when looking for science or maths teaching position - despite for instance featuring heavily in senior managerial posts in industry. It may be what the IEI is getting at.
To get a permanent teaching post in a secondary school in Ireland or the UK, you need a Postgraduate Diploma in Education (PGDE), what used to be called the H-Dip. That’s in addition to your primary degree. I don’t know what Engineers Ireland are on about tax breaks for.
An engineer who is long enough on the dole can apply to a Back To Education Allowance which will fund his or her H-Dip plus pay them the dole while they’re at it. The PGDE is one of the only postgraduate courses funded by the BTEA. As long as they have a good enough degree, and a good honours degree will put them way ahead of the usual pass degree PGDE crowd, they should easily qualify.