It is common for rewiring and replumbing to happen at the same time as part of a renovation project. If the house has more than 4 bedrooms, then you should be ok to invite both trades to work on the property at the same time. However, if you're property is smaller, than you may be better staggering the work. Simply because we are both trying to work in the walls, laying cables and pipes so we can get in each others way and slow each other down.