Chili:
I don't know the airfield in question, but I disagree - we do NOT have enough information here to answer definately.
The information we have been provided with seems to indicate that gliding and powered operations are totally seperate, with the powered aircraft operating in this case on the north side of the airfield while the gliders take the south. If this is the case (and I'm not saying it is - I don't know), then a base leg join, to fit in with the segregated power traffic, could well be perfectly acceptable.