RWS-7 on UP Metra Line

I was near downtown this morning and saw a movement of RWS-7 moving slowly (10mph) on the elevated ex CNW tracks between Western Ave and Halsted.

Any idea of what this was? Kinda looked like a rail grinding operation, except nothing was happening.

ed

I saw it this evening (april 24, '09), stopped on the main line next to the coach yard. Can anyone confirm it’s purpose? Looked like a train from hell.

I’m sorry to display my ignorance here , but I’m having difficulty locating a picture of an RSW-7. Google only brought me back to this forum. What am I missing for the internet query? thanks