Correct, but judging by his description of the situation, that will not be the case. The FW blocks outgoing connections to said port - just putting a proxy on his workstation that does nothing but pass on the connection using HTTP CONNECTs will not make the least difference to the FW. To the FW, it's still an outgoing connection originating on the inside network.
Or perhaps the company proxy he installed has a way to negotiate outgoing connections with the firewall, in which case your statement is of course correct.
CU
Robartes- who just occasionally tends towards the pedantic ;)