On PMTC, PoW operations are processed by central servers without receive any reward for it.
do you mean the block reward is distributed by central server to each address?
On testnet network and first steps of mainnet, central servers perform the mining task, and the reward is sent to the block winner selected among all stakers.
In future (when our software is robust enough), we plan to make it open source and implement masternodes, and they perform the mining task getting a reward shared with stakers.