Subject to, will bank enforce due on sale clause?

[Simon Stahl]

I wanted to look into the possibility of purchasing properties subject to existing mortgage. From all I read in the web and here on BP, banks are usually not enforcing the due on sale clause as long as the payments are made in time. But now I talked to a RE lawyer and she says subject to does not work because the banks WILL enforce the clause. 

Did anyone try this in the past one or two years? Can anyone confirm that it works or not works?

Simon