Ralph,

It would appear, at least for a Small Quantity Generator, that a cell phone alone does not meet the requirement.  (see text below)

Note that when I quickly scanned the guidance document for (Michigan's) Very Small Quantity Generators there is no mention of telephones being required.

Some general thoughts:

- Not everyone, even in this day and age, carries a cellphone

- Some labs, especially with proprietary research, animal research, and other sensitive research may prohibit cell phones

- Cell phones may not work in some buildings and some areas of the country may have different area coverage by different phone carriers.

You might consider centralized "emergency" phones in the hallway that (only) ring 911.

From the Federal Register:

b. The meaning of “immediate access.” Preparedness and prevention provisions include the condition that, whenever hazardous waste is being poured, mixed, spread, or otherwise handled, all personnel involved in the operation must have immediate access to an internal alarm or emergency communication device, either directly or through visual or voice contact with another employee, unless such a device is not required. At issue is whether the phrase “immediate access” is clearly understood or whether additional clarity is necessary. EPA proposed to modify this language to include the parenthetical “(e.g., direct or unimpeded access)” after the phrase “immediate access.” EPA requested comment on the usefulness of modifying this language.

The majority of commenters supported this modification, although one commenter expressed concern regarding what would constitute immediate or unimpeded access. Another commenter requested clarification as to whether access to a cell phone satisfies the requirement for immediate access to an alarm or communication device. [Bold my emphasis] EPA believes that, although cell phones are a useful means of communication, they should not be relied upon solely to satisfy this requirement. The Agency is therefore finalizing § 262.16(b)(8)(iv) and § 262.254 as proposed.

Also see:

 § 262.16(b)(8)(iv)

Access to communications or alarm system.

(A) Whenever hazardous waste is being poured, mixed, spread, or otherwise handled, all personnel involved in the operation must have immediate access (e.g., direct or unimpeded access) to an internal alarm or emergency communication device, either directly or through visual or voice contact with another employee, unless such a device is not required under paragraph (a)(8)(ii) of this section.

(B) In the event there is just one employee on the premises while the facility is operating, the employee must have immediate access (e.g., direct or unimpeded access) to a device, such as a telephone (immediately available at the scene of operation) or a hand-held two-way radio, capable of summoning external emergency assistance, unless such a device is not required under paragraph (a)(8)(ii) of this section.