I cant see a prob with whats been done , they may not have intent to undercut other w/cs , they might just be cheap , that said , if they knew your price and did it on purpose then thats a bad show .
I remember when i first started out , ladders only , i was up at a window working away and a car pulled up , more ladders on the roof than you could shake a stick at , then a team of 4 got out and did leaflet drop right in front of me !
I had 17 of the 22 houses in the street and i did not lose a single one to them .
If you do a good job then dont worry , after all if they do get your work its obvious that they will put prices up to same as you within a year anyway , then you will probably get them back again , if you want them that is .
Rich P @ F