There's not a 'general rule', which is really what the problem is. The legislation isn't really specific enough in terms of what 'counts' as an available vacancy. If it was more of a restructuring and the jobs were changing, so it was deciding who gets the new jobs, then you'd have a stronger argument.
I've always been given (and given my own clients) the advice that if there is a situation where you are choosing between two suitable candidates for one job, even if the job is the same as the jobs the individuals already had, and one of the individuals is on maternity leave, then she should be offered the job.
Others take a harder view of what constitutes a 'vacancy', some saying that the job must be different in some way, and others going further and saying it literally must be a completely separate job vacancy in for example another department or whatever, nothing to do with the restructure.
So you do have an argument but it's not as clear cut as it might be. Your argument is definitely stronger as you are being asked to 'apply' for the jobs, in other words you are not just being selected for redundancy, it's more that they are selecting people for the jobs using a job application process.
I'd suggest you write to them drawing your attention to Reg 10, saying that you understand you should be offered suitable available jobs, and as the two jobs are at present available until the applications have been considered and selection has taken place, you would like their confirmation that you will be offered one of them.
Worth a try at least. They may say yes, they may say no the jobs are not vacancies, at which point you can decide whether or not you wish to take it further. As I say, the fact that they are asking people to apply certainly implies they are considering them 'vacancies' until the process is complete.
Do you think if you applied along with the others you wouldn't be successful?