Will e-mail still get bounced if their mail server has a poor senderbase reputation?
Unfortunately yes because the server reputation check is done before address-based options are processed.. It's possible for the server to have its reputation reset by Plusnet, but that would only be effective if whatever led to the poor reputation has been dealt with.
Additionally the whitelisted address or domain needs to be the bounce address/domain shown in the return-path header, which is not necessarily the "From" address. However determining that needs a sample message to reach you.