No, you can only bolster Ruins in your deployment zones. Aegis Defense Lines are Fortifications/Battlefield Debris.
See the Space Marine FAQ
Page 71 – Techmarine, Bolster Defences.
Replace this entry with the following:
“Bolster Defences: Techmarines can increase the effectiveness
of cover, reinforcing crumbling walls and re-welding badly
damaged spars. After deployment, but before Scout
redeployments and Infiltrate deployments, nominate a single
ruin in your deployment zone. The ruin’s cover save is
increased by one for the duration of the game (usually to a
3+). Each ruin can only be bolstered once”.