Test lead is involved in preparing test plan
test entgineers are no way related in preparing test plan
role TE is testcase design ,and execution and bugtraking 
and reporting them

Genarally TL is involed in preparation of the TestPlan.But 
it is not mandatory only TL will take main part in the 
preparaion of the TP.Test engineer can suggest to TL,if he
(or) she has good understanding on project and resources,if 
he or she has more exp with the project,if TL is wrongly 
given deadlines.If your suggestions are valid,TL will 
incorporate all of them to the TestPlan.But in most of the 
companies Test engineers are just audians.

Test Plan inculdes the scop , approches , resources , 
schedule of the testing. As well as it inculdes the 
following things :

1. What to be tested 
2. What will not be tested.
3. What are the deliverables . 
4. What is the H/w & S/w combination required for testing 
that particular application. 
5. What is the individual & organisational responcibilty 
during this testing.