I suppose 'every bit helps' but, in a nutshell, 'no'.
Having reported my bike stolen and having handed in a lost/stolen bike (so I could recover it under finders/keepers rules) I am familiar with the backwardness of the whole Police process of dealing with stolen bicycles. Last time I went through the hoops the concept of 'mountain bike' was new fangled - you could specify rod or caliper brakes but not cantilevers, never mind disc or 'v'. Frankly it is a miracle they ever repatriate bikes due to visual identification. Given this one would expect that the 'Datatag' would be exactly what everyone apart from the thief needs...
I also know that 'Datatags' are definitely not what you might call a hot seller in bicycle shops - they might be in the motorbike world but bikers only put them in because they have to be insured. If they were that good then people would be queuing up for them, as it is they just collect dust in bike shops that actually stock them. This means that they are not in common circulation. This affects the likelihood that the Police will check for them as well as their deterrent effect to thieves.
The likelihood of your tagged bike being found by the police is going to be slim, only if it gets handed in are you likely to benefit from the Datatag and that is assuming the Police have one of those scanners anyway. I have not heard of these things working - there is a complete absence of anecdotal evidence on the internets too. I think that 'Datatag' stickers are a bit like car alarms in that nobody takes them seriously except for insurance companies. This is no criticism of 'Datatag', the product they make and the goal of the product, it is just that there is a big difference between the marketing theory and the practice.
That said, I do have faith in the new Bike Register scheme and have my bike tagged by the Police. Most Police do have days in the town centre where they mark bikes up for free.
Given that the scheme is free and endorsed by them you have to wonder why bother with any other scheme, particularly if there is practically no evidence of it having ever worked.
You get stickers with Bike Register and you put all your details with them, an improvement on postcoding.