The dogs in the 2005 movie are not related to Lassie, although the Official Lassie does have a cameo.
In 2003 the Weatherwax family ended their incredible long run of supplying line dogs to portray Lassie that started in the 1940's with Rudd and Frank Weatherwax and The Studio Dog Training School. This followed a sale of the Lassie trademark from the Weatherwax family to Classic Media. In 2004 the movie deal came up and there was no line dog and trainer under contract. By the time filming was slated to start, an agreement was reached between longtime Weatherwax co-trainer, Carol Riggins and HeyHey (the FIRST 9th generation direct descendant dog selected to be Lassie in 1998). However, quarantine laws would not allow Lassie into the country in time for filming. The locations, actors, crew, caterers and everything in between were ready to go and Lassie couldn't get there. There was not one line dog in the US that could get in to shoot the movie.
Birds and Animals supplied the dogs for the 2005 movie and there are 3 dogs. The main dog was named Mason, and there were 2 stunt dogs. The Official Lassie has a cameo shot in the kennel scene. That was shot by Carol Riggins and HeyHey in Los Angeles on blue screen and inserted into the movie.