These CMH lamps have completely different names in Europe and in North American despite that they manufactured by the same company: Philips Lighting.
The name of the lamp in Europe is CosmoWhite CPO-TW and in North America: Cosmopolis CosmoWhite.
Why?

For this you will have to ask Philips marketing guys.
But it is not the first time the same produc bear different name on different places of the globe (other cases are e.g. Volkswagen Golf/Jetta)...

Anyway the German product website puts it in such a way that "CosmoPolis" is a complete lighting system, consisting of both a lamp called "MASTER CosmoWhite" and an electronic ballast.

The description is worded in a way that later further lamp variants could be launched, too.

Perhaps Cosmopolis White is the original name of these lamps and in Europe, Philips changed their name to Master CosmoWhite CPO-TW immediately when they started to market these lamps, while in the US, the original name was retained, much like that was happened with the Philips Marathon CFLs which their name was changed to PLE-T in Europe immediately when Philips started to market these lamps, while in the US, the original "Marathon" name was retained.

Originally, the CosmoPolis Outdoor CPO lamp family had two members:

1) a ceramic metal halide version called Cosmo White (2800K), also known as the TW version: Tubular White. Initially named CPO-TW, now CPO-T. It comes in 4 different lamp powers: 45W, 60W, 90W, 140W. Color code: 728, 45W: 628.

2) a ceramic high pressure sodium lamp with improved efficacy, called Cosmo Gold (2000K), also known as the TG version: Tubular Gold. It was named CPO-TG and came in 2 lamp powers: 65W and 140W. Color code: 220.

The CPO-TG version was soon dropped from the Cosmopolis family portfolio and only the CPO-TW version remained and was renamed CPO-T.Maybe, there are still future plans to re-introduce the TG in Europe and hence the need for the CosmoWhite name in order to differentiate within the Cosmopolis family while there are no such plans for the US? I'm just guessing here.

Then again, it might also be due to legal reasons, availability of expensive lawyers and potential threats of lawsuits that made Philips decide to use the term CosmoWhite in Europe and CosmoPolis in the US

http://www.lighting.philips.com/gr_el/applications/urban/pdf/cosmopolis%20leaflet_english_april06_final_.pdf

http://www.scribd.com/doc/20258082/Lighting-Handbook-Perfect-Light-by-Night

I could also imagine that it has something to do with marketing. The German presentation strongly emphasizes the white light and how it looks much more beautiful than HPS. Probably they found that only this argument suffices for introducing a completely new system. Incompatible HPS lamps do not appear to be a promising product to me.

Btw, Cosmopolis is amongst the options for a number of luminaires made by Leipziger Leuchten, the former LBL.

I perfer HPS any day of the week, The white light from the cosmopolis maybe appealing to some people however the stupid electronic ballasts are a big put off to me! ballasts rated to 50000 Hours, even if they last that long after 2 lamps the ballast is dead. Its pathetic. On the street lighting in my area they have old magnetic ballasts that date back to the 70s and still going. Some of them the wooden back board has rotted out and the ballast hangs by cables in the bottom of the pole down past the inspection hatch (gear in base) and they STILL WORK The new cosmowhite lamps they put in..Some only last a couple weeks then the ballast goes pop.
  I am currently running a 60w Cosmowhite on a 70W SON gear running vertical just to see how it lasts!