They have listening station there nothing more AFIK...should not take a lot of effort to knock that out if it came to it. India should not be paranoid about every single Chinese move.
You have got right..the string of pearls is not a military option.Does anybody seriously think that Sri Lanka or Bangladesh will host Chinese naval ships in a conflict with India?
What it will do is ensure continuous movement of goods to China on civilian ships...India can hardly attack a Sri...
These are minor issues..India and Nepal share a history which is beyond what most nations do..be it religious or cultural.They also have an open border and Nepalese don't need any visa to stay and work in India(and millions stay in India) and even join the military.Not even the US and Canada...