A simple overview in Nature World News - [link] found that after tagging over 960 badgers in Kilkenny, the researchers noted:
"On average, the badgers were found just 2.6km from their dens, but 5 percent of those tagged were found more than 7.5km away from their dens, with the longest having made a 22.1 km journey."In old money, that is an average of 4.6 miles for the 5 percent of the tagged animals moving away from their home base with the furthest long distance hop measured at 13.70 miles.
No mention is made of a return ticket.
And in Owen Paterson's Parliamentary written questions, tabled a decade ago now, the reason for these 'long distance' travels was described thus:
"Research conducted by the Central Science laboratory has identified behavioural differences between badgers excreting M bovis and uninfected animals. Badgers excreting M.bovis had larger home ranges and were more likely to visit farm buildings."23rd March 2004 Column 684W 
The Irish research appears to confirm this, but goes further with some staggering statistics on infectivity:
"In lower-density populations, infection may be seeded, or disease prevalence maintained, in relatively isolated populations from dispersing badgers (Hardstaff et al. 2012). [snip]
However, this speculation must be considered against a backdrop of high bTB badger prevalence in Ireland (36%; Murphy et al. 2010) and parts of Britain (35–53%; Carter et al. 2012).
Given our findings, we would expect that 5% of badger dispersal attempts in this population would be at distances of 7·3 km over a 4-year study. This would indicate that, in the absence of physical movement barriers, buffers of ≥7·3 km may be needed to restrict inward dispersal and maintain site independence with a high degree of confidence.We get the picture .... which we've seen many times before.
Up to 53 per cent of GB's badgers now carry zTuberculosis. (Carter et al- 2012)
When they achieve 'super excreter' status - or even before - these highly infectious animals make long distance hops in an attempt to find sanctuary and die.(PQ 158375]
And these mobile time bombs can range an average of 'more than 7.5km from base, with the longest recorded at 22km.'
This can 'seed' strains of M.bovis in previously uninfected areas.