Ma Bell's version of long-distance may only be the next best, once-removed, thing to being there.

Southern Pacific Communications, a subsidiary of the railroad company that recently announced plans to move to Montgomery County, now offers off-hours long-distance dialing for as little as half of Bell's rates. This discount "Sprint Ltd." service is open to subscirbers between 5 p.m. and 8 a.m. weekdays and all day Saturday, Sunday and holidays.

Sprint Ltd, is an extension of Southern Pacific's existing national business network. Consequently, the Sprint service is available in Washington and 65 other major metropolitan areas throughout the country.

Company officals decided in August that because "we have our own network sitting out there and littel traffic in the off-hours," an effort should be made to capture a share of the consumer market. The Sprint service was initiated in the middle of October.

The decision was possible because of a 1978 federal court ruling that AT&T has no monopoly on the long-distance market and must provide interconnect facilities to competitors.

A Sprint customer pays a $10-a-month subscriber charge for a special phone number and access codes to Sprint cite. The customer, who must use a touch-tone-type phone, calls the Sprint number, then the city code and finally the number he is trying to reach.

Rates are between 40 percent to 50 percent cheaper than Bell's between the hours of 5 p.m. and 11 p.m. and approximately 25 percent less than the after-11 p.m. night rate.

An AT&T spokesman says the company is not particularly concerned but is "carefully watching" Southern Pacific's offering.