It doesn't sound like BMW Hong Kong's problem. First Registration Tax is collected by the government, I think the ball is in their court to refund the excess paid.
I think BMW Hong Kong should probably help process the refund since they collected the money in the first place, but thats it...
E92 335i 6MT | Balloon White | Black Dakota Leather - Sold
PROcede Rev3 V5 | AE Quad Exhaust | BMW Performance Short Shift Kit | Gunmetal 19" M3 GTS Wheels | BF Goodrich g-Force T/A KDW 2 | AST 4100 Coilovers | Swift Springs F:280 R:560 | ER Charge Pipe | Tial Blue BOV | VRSF 3" Downpipes | VRSF 7" Intercooler