I have seen thermostat cable used to feed remote emergency lights from remote capable emergency lighting units. Although the batteries only provide 6 volts, it seems that having t-stat cable in the same enclosure as 120 volts would be a violation, unless the t-stat cable is rated for 120 volts per 300.3(C)(1). I haven't been able to determine the voltage rating of the t-stat cable(no marking).
Redsy: Usual remote wiring methods are 'Chapter 3 methods', as the rest of the job, with the same cable/conduit. VD is a definite issue. The instructions that come with the item should specify/suggest/reccomend the ga of conductor required, based on the circuit length.
I see you said 'capable' in your OP. A few guys try to tap off of the LED exit units! 90 min test? Forget it.
Also, 700.16, second paragraph ('05 NEC) is enforced.
Years back, two country clubs were big into remote em ltg, and 'did not want the battery box visable to the members. Some runs to the heads were 150'; (# 6 & #8)
I'm talking specifically about an exterior remote head driven by a remote capable combo unit on the wall immediatley inside. Voltage drop would not be an issue at 3-4 ft.
I saw 150-volt t-stat wire in Graingers.
If the t-stat wire is rated for the higher voltage in the combo unit, I don't know if I can find a code-related issue. A possible issue may be a non-metallic wiring method above a drop ceiling in a commercial bldg., but it is Romex that is specifically prohibited in that case.
Note: I am not advocating this practice. I have debated it with another contractor, and am asking for opinions.
Redsy: For debate reasons, I throw into this thread...Article 720 (2005 NEC): 720.1 Under 50 v, AC/DC 720.2 N/A, as it is egress lighting, not any referenced. 720.3 N/A 720.4 Conductor size minimum (#12)
Based on this, IMHO, you need #12 t'stat wire, rated 150 volts or higher from your OP. Based on that...why bother?