Roy Scheider is a farmer who won't let a locomotive bearing nuclear weapons pass through his land in "The White Train," to shoot in Texas in September. . . . Andy Garcia, hot from sharpshooting in "Untouchables," plays a Spanish revolutionary poet in exile overseas who ponders returning home and running for President in "Latin Roulette," which films in London next month. . . . Singer Maureen McGovern plays a woman who auditions with her daughter for a talent show spot and discovers she can't sing in the "Tracy Ullman Show." . . . Ben Frank is a porno agent who gets starlet Jonna Lee to do X-rated films over the objections of her conservative mother Melinda Dillon in the CBS TV-movie "Mourning Song," now shooting in Phoenix. . . . Christine Lahti and Judd Hirsch are married radicals involved in the '60s underground movement whose son, River Phoenix, is fearful they will be exposed once he enters college in "Running on Empty." Sidney Lumet directs in NYC Aug. 3.