How to set different metrics for routes learned by a single source of Redistribution ?

Good Question. This can be done by using route map  in the redistribute command, where the route map will decide what metrics to assign to which routes by refering an access-list. Here's an Example:

router ospf  1redistribute eigrp90 metric60 subnets route-map ASSIGNnetwork  160.10.0.0  0.0.0.255 area1network  12.10.2.0  0.0.0.255 area0default-metric  30

access-list11 permit  10.1.1.0  0.0.0.255

route-map ASSIGN permit  10  match ip address  11  set metric  100

route-map ASSIGN permit20

 Another possible method is using Offset-list.

metric-value -the metric is the Multi-Exit-Discriminator (MED). Valid values are integers0 to.

Use the set metric command to define the metric used when advertising routes via BGP. Metric values set with this command override the default metric value for this route.

Use the no set metric command to select the default metric for this route.