Get attribute from touching line layer (QGIS)

I have two line layers. The features of both are touching each. Now I would like to label one of the line layers with the attributes of the touching layer.

The case: In the one layer are drain's (green) and in the other one are cables (red). The cables are inside the drain (digitized with snapping to the drains). Now I need the drain-id (green labels) labeled on every cable.

I have to use shape files! So I thought to use the aggregate function of QGIS...

Answer

You can use RefFunctions Plugin together with this expression:

 geomintersects('drain','drainid')

'drain' is the targetlayername and 'drainid' the targetfieldname you want to get.