In presence of multiple possible paths, this is a tentative to force a destination through one path and the other through the other path. The trick is to just use a static route with a next-hop that should be resolved to the directly attached transit provider. This assumes AS paths and local preference between the transit providers are the same.
However, this doesn't work as if a transit provider goes down, the attached router will still advertise a most specific route which will be picked by the neighbor router:
[edit]
juniper@router# run show route table router1.inet.0 198.51.100.34/32
router1.inet.0: 10 destinations, 11 routes (10 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
198.51.100.34/32 *[BGP/140] 00:04:46, localpref 100
AS path: I, validation-state: unverified
> to 192.0.2.1 via lt-0/0/0.1
[edit]
juniper@router# run show route table router2.inet.0 198.51.100.34/32
router2.inet.0: 10 destinations, 11 routes (10 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
198.51.100.34/32 *[Static/5] 00:04:50, metric2 0
> to 192.0.2.0 via lt-0/0/0.2
There is a tentative to not redistribute the route into BGP in this case, but it seems next-hop is the protocol next-hop, not the resolved one...