Is there a problem planting a salix caprea pendula (weeping pussy willow near foundations or drainage pipes?

I would be careful of planting any tree near to foundations or drainage pipes. All willows are particulary demanding of water and so I would keep it well away from both.

You are right to question this! A willow, any willow, will 'smell' a water source and it's roots will head straight for it. Believe it or not they will get into the drainage and cause you a finacial nightmare.

I had one in my front garden (planted by previous owner). Because its growth is so topheavy it snapped during a gale. Unfortunately the area around it was laid to lawn and it probably had a year's head start with leftover bits of root still growing before I started to notice the suckers. I still dig up bits of root from time to time after some five years. I don't know if it got into the drain or not but I wouldn't have one in my garden again.

In a word,'yes'
All willows have extensive suckering root systems and as such will force their way into any weak joints or cracks in pipes and foundations.