as far as my knowledge in concerned you can't board on a train with a Wait-listed ticket untill ur ticket upgrade to RAC... that's why e-ticket auto cancel ho jata hai waiting list rehne pe..
lekin log PRS tickets leke journey to kar hi lete hain.. so i-ticket bhi PRS se counter se print hokar aata hai i guess aap use kar sakte ho.. lekin agar TTE ne train se utar diya to aap kuch nahin bol sakte as that's in rule..
all the best..